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Linux uio interrupt example

dts as an example - update it according to your setup. For cards that don't generate interrupts but need to be polled, there is the possibility to set up a timer that triggers the interrupt handler at configurable time intervals. This is the second article in the series — please read “Writing a Linux Kernel Module — Part 1: Introduction” before moving on to this article, as it explains how to build, load and unload loadable kernel modules (LKMs). . UIO example system using AXI GPIO with connected PL to PS interrupt. Things to know about uio_hv_generic¶ On each interrupt, uio_hv_generic sets the Interrupt Disable bit. Documentation about UIO is available in the DocBook format in the kernel Documentation/ 5 New features in Linux 2. This document presents a Linux-USB “Gadget” kernel mode API, for use within peripherals and other USB devices that embed Linux. The directory structure of the archive is outlined Xenomai, however, does also allow interrupt handling in user space. Iperf, Netperf and hping3 was used to measure network performance. For example, linux uses ttc (trimple timer counter) as tick timer in zynq series soc. The Linux kernel provides a userspace IO subsystem (UIO) which enables some types of drivers to be written almost entirely in userspace (see basic documentation here. d/. It is not always necessary to write a device driver for a device, especially in applications where no two applications will compete for the device. I don't understand why I have not node /dev/uio0. > Via ioctl it provides a mechanism to map MSI-X interrupts into event > file descriptors similar to VFIO. which do not support the Interrupt Disable Bit in the command register. For example, if you unbind an NVMe device on Linux, the devices corresponding to User space drivers utilize features in uio or vfio to map the PCI BAR for the device into SPDK polls devices for completions instead of waiting for interrupts. UIO_MEM_VIRTUAL is memory in the kernel virtual address space - the space used by vmalloc_user() and friends. Application. UIO frame work also allows the application kernel driver to register interrupt handler with hardware IRQ and wake up the user space daemon upon hardware interrupt. 1. x. c as an example. There are two distinct UIO device drivers provided by Linux in drivers/uio UIO Driver (drivers/uio. 1 EDMA3 LLD The EDMA3 low-level driver (LLD) is a set of APIs that supports programming the EDMA3 peripheral. Linux now offers an exceptionally robust environment for driver development: with today's kernels, what once required years of development time can be accomplished in days. The userspace driver should clear this bit before blocking and waiting for more interrupts. k. UIO_MEM_LOGICAL is memory in the kernel logical address space, such as that returned by kmalloc(). Get the corresponding System Interrupt number for the Interrupt number obtained in step 2. The generic interrupt handler of uio_pdrv_genirq will simply disable the interrupt line using disable_irq_nosync(). ). Post navigation ← How to Design and Access a Memory-Mapped Device in Programmable Logic from Linaro Ubuntu Linux on Xilinx Zynq on the ZedBoard, Without Writing a Device Driver – Part One Microsoft Catapult at ISCA 2014, In the News → Writing a Linux Kernel Module — Part 1: Introduction, and; Writing a Linux Kernel Module — Part 2: A Character Device, before moving on to this article, as those articles explain how to build, load and unload loadable kernel modules (LKMs) and character device drivers. Dear Experts I need help regarding interrupt handling using UIO. It is used in the Linux multimedia architecture for SH-Mobile, and an example will be given for managing an image rescaling and colorspace conversion hardware unit (VEU). The file offset shall be incremented by the number of bytes actually read. 24 release. c) – For more advanced users as a minimal kernel space driver is required to setup the UIO framework – This is the most universal and likely to handle all situations since the kernel space driver can be very custom There are two distinct UIO device drivers provided by Linux in drivers/uio UIO Driver (drivers/uio. You need to manage the IPI. , HW_RD_REG32(0x4b220000), Linux needs memory mapping of memory regions to user space, and this is done using the UIO driver with linux file-I/O like API such as open(), close(), read(), write(), and etc. LWN. at the Dept. DPDK userspace interrupt notification and handling mechanism is based on UIO/VFIO with the following limitations: Per queue RX interrupt events are only allowed in VFIO which supports multiple MSI-X vectors. In other words, userspace drivers are not new. can find them in zynq datasheet, and also in example code for interrupt UIO. Each driver provides attributes that are used to read or write variables. * interrupts. Instead, the interrupt handler simply disables the: 256 * interrupt in the interrupt controller. It is defined in <asm-alpha/machvec. 950 </para> 951 <para> 952 On each interrupt, uio_pci_generic sets the Interrupt Disable bit. On files that support seeking (for example, a regular file), the read() shall start at a position in the file given by the file offset associated with fildes. Unix, Linux, C and other notes. The following is an example of running the dd command on a Linux host system: zynq-uboot> <INTERRUPT> UIO — Mostly fanned out from PL . General Purpose Input or Output: a generic I/O line on a SoC is often referred to as a GPIO. The problems raised by multimedia applications running alongside normal applications is discussed. il Tk Open Systems June 27, 2011 This work is released under the Creative Commons BY-SA version 3. An additional key-value pair needs to be added to the Linux boot arguments. We introduce UIOMux: a resource management layer for UIO devices, providing fine-grained locking, memory management and interrupt dispatch. The userspace driver should clear this bit before 577 blocking and waiting for more interrupts. Verify the PF PCI address prior to representors creation: The cifX Device Driver for linux, is splitted in a kernel module and a user space library. The most common example are x86 ioports. For this we use the segment selector to index into GDT/LDT where we can find the corresponding segment descriptor. What’s the device tree good for? 1. Interrupts Example Program in Linux Kernel ; you should keep these following points in your mind. This example uses 3 system calls per interrupt due to limitations in generic-uio. The value will match the compatible string in the device tree node for the UIO {"serverDuration": 38, "requestCorrelationId": "00ccb9e3b659386a"} Confluence {"serverDuration": 38, "requestCorrelationId": "00ccb9e3b659386a"} This entry was posted in ARM-SoC-FPGAs, FPGAs on May 28, 2013 by Jan. 953 This prevents the device from generating further interrupts 954 until the bit is cleared. Now, edge-triggered interrupts are a _lot_ harder to mask, because the Intel APIC is an unbelievable piece of sh*t, and has the edge-detect logic _before_ the mask logic, so if a edge happens _while_ the device is masked, you'll never ever see the edge ever again (unmasking will not cause a new edge, so you simply lost the interrupt). Indicate device memory regions to user space. C library interrupts. Installing an Interrupt Handler | 261 predictable (for example, vertical blanking of a frame grabber), the flag is not worth setting—it wouldn’t contribute to system entropy anyway. Originally, Russell King identified different types of handlers to build a quite universal set for the ARM interrupt handler implementation in Linux 2. The examples assume that the Xillinux distribution for the Zedboard is used. With a kernel module, only 1 system call per interrupt would be required for this hardware. In the above example, virtio port 0 in the guest VM will be associated with vEth0, which in turns corresponds to a physical port, which means received packets come from vEth0, and transmitted packets is sent to vEth0. userio accomplishes this by allowing any privileged userspace program to directly interact with the kernel’s serio driver and control This example uses 3 system calls per interrupt due to limitations in generic-uio. 6 Training lab book Patching the kernel is needed because The PRU application loader for Linux is a software tool which can be used to load a binary to PRU’s memory area and to manage the code executed in the PRU from the user space. On ARM all device tree source are located at /arch/arm/boot/dts/. I've > extended the GPIO/UIO drivers (mostly gpiolib. But after boot my /sys/class/uio directory is empty and I have not node /dev/uio0. linux. This is done by via a character device that the user program can open, memory map, and perform IO operations with. By definition a GPIO is a line that can be used as an input or output. uio_pci_generic detects this support, and won't bind to 949 devices which do not support the Interrupt Disable Bit in the command register. Now let’s find out device names using some different command-line tools as shown: Find Out Plugged USB Device Name Using df Command. Linux provides a standard UIO (User I/O) framework for developing user-space-based device drivers. When the interrupt kicks in, the UIO driver interrupt handler will notify the poll function that will wake up the select. In this mode the user space driver is responsible for acknowledging and re-enabling the interrupt. In this video and the following 2 or 3 videos we create a vivado design that contains GPIO, I2C and SPI interfaces for ZCU102. And I don't care one whit if it happens to work on parport with an old legacy ISA interrupt that is edge-triggered. “Get me a laptop, and tell me about the x86 hardware interfacing experiments in the last Linux device drivers’ lab session, and also about what’s planned for interrupt is serviced, thus simplifying shared interrupt handling. 5 . h> file, which interfaces to the input subsystem. The User Space IO (UIO) driver model enables drivers to run in the user space of a Linux system [4]. Interrupt support only available for devices handled through uio_netx kernel module Linux UIO (user-space IO) functionality allows interrupt delivery to user-space programs via the Linux file IO framework. New training The mechanism for generating an interrupt from a PRU to the A8 (host) is well-documented. Interrupt under a timer throttling (interrupt per 500us) OS. This is NOT automatically done inside the driver / toolkit. Skaali, Department of Physics, University of Oslo FYS 4220/9220 - 2011 - Lecture #5 16 VxWorks ISRs (VxWorks Programmer’s Guide) 2. 789645] Created Jailhouse cell "linux-inmate-demo" [ 1781. This interrupt is mapped to channel 2, then host 2 which goes to ARM interrupt PRU_EVTOUT0, which is ARM interrupt 20 (see TRM 6. If the event has not been sent then any code which attempts to read from that file will simply block (wait Recently I've been spending a little bit of time learning about FUSE, CUSE, and UIO, which are related technologies for user space device driver implementations in Linux. 13. Module Size Used by sha1 3 UIO Driver Each UIO driver consists of two parts – small kernel module (the need for it is mostly because of device-specific interrupt handling/disabling) and user-space driver logic (as shown in figure 1). This will be a simple article about Linux Device Drivers, in fact about a char driver that controls the GPIO ( General Purpose Input-Output) port of the Beaglebone Black. </para> <para> On each interrupt, uio_pci_generic sets the Interrupt Disable bit. We can then check for the interrupt using the “select” function. I'm trying to convert an existing . then check if anything was written to it during " unsuccessful boot", it could be just a network problem for example. IRQ stands for Interrupt ReQuest and refers to special numbered channels that are used by devices to get the processors attention. +interrupt, it's your modules task to determine the irq number during +initialization. dtb) is produced by the compiler, and it is the binary that gets loaded by the bootloader and parsed by the kernel at boot time. It offers you the option of dynamic allocating a number of memory regions (the number and the size should be specified at boot time) when the uio device is opened. The return value from container_of() is a pointer to the corresponding container type. Generated on 2019-Mar-29 from project linux revision v5. Linux-2. The paper is a case study of working implementations of soft real-time features for Linux. The device has several IRQs and have requested them on my driver: irq = platform_get_resource(pdev, IORESOURCE_IRQ, 0); rc = request_irq( UIO drivers. Libmetal does not provide IPI drivers. Xilinx Zynq Ultrascale+ MPSoC IPI On files that support seeking (for example, a regular file), the read() shall start at a position in the file given by the file offset associated with fildes. User-space programs waiting on epoll() or select() function calls on UIO file descriptors are woken up when the interrupt is generated. GIC Metal_init() Register IPI device and shared memory to libmetal – This Step is for Baremetal/RTOS only, as they are specified in the device tree for Linux. Note these examples use the ARM processor and the PRU Application Linux Loader to initialize the PRU and may vary from the examples on Interrupt translation domain; responsible for mapping between GPIO hwirq number and linux irq number irq_base first linux IRQ number assigned to GPIO IRQ chip (deprecated) irq_handler the irq handler to use (often a predefined irq core function) for GPIO IRQs, provided by GPIO driver irq_default_type DDEKit and DDE for Linux. 13 May 2018 With the Xilinx Concat IP interrupts from IP cores / FPGA are collected The IRQ will also be enumerated in Linux the same order as they are in the IP. x) OpenAMP Application Example Structure –system initialization Initialize application, system specifics – E. 0 and net device name enp3s0f0. In order to enable the interrupt check, we need to write a signed 32 bit int value “1” to /dev/uio0. Right now the UIO core is working and in the [-mm kernel releases][mm]. A an interrupt occurs, the process waiting 03 #include <linux/uio_driver. It might be desirable to add an ioctl() call to the UIO driver which simply blocks until the interrupt count is at least 1 more than the last call, leaves the interrupt 2. AVR code for controlling LEDs with button by external interrupt and shift register “74HC595” This example is Memory management is an essential aspect of every System Administrator to improve the performance of a Linux system. On Wed, Sep 30, 2015 at 03:28:58PM -0700, Stephen Hemminger wrote: > This driver allows using PCI device with Message Signalled Interrupt > from userspace. Linux graphics course. 25-rc9. - Source code basic interrupt handler Demonstration Module 8 - introduce uio device. The Linux family of operating systems is based on this kernel and deployed on both traditional computer systems such as personal computers and servers, usually in the form of Linux distributions, and on various embedded devices such as routers, wireless access points, PBXes, set-top boxes, FTA receivers Interrupt notification for applications An example stand alone server is offered with the linux driver. b. 8. what's the best simple way to drive a new IP core in PL from Linux? Zedboard forums is currently read-only while it under goes maintenance. Interrupts are handled using the Interrupt Disable bit in the PCI command register and Interrupt Status bit in the PCI status register. One thing I will highlight relevant to your example is that we only support interrupts that are ultimately connected to IRQ_F2P[0] - this is due to how the Linux drivers are configured in the stock image. 5/2. As far as I can see there isn't a way to name the /dev/uio%d device file to something more useful, is that so? I would like to name the device file from within the kernel so I The IPI (Inter Processor Interrupt) interrupt can be used for notification of messages between processors. backport into 2. e. Linux is provided openly by most vendors of FPGA who have gone down the route of hard coding an ARM processor into the device (ASIC area). B. In fact, the kernel configuration process consists mainly of choosing which files to include in the kernel to be compiled. After you are able to use this example, you may break the loopback and insert  Linux provides a standard UIO (User I/O) framework for developing or even that I've run more than some examples on my BeagleBone  2 Apr 2013 + "generic-uio". Hello everyone, i'd like to use an interrupt from a pushbutton. The device-tree of_id of the uio driver has to be set via kernel command line Add "optargs='uio_pdrv_genirq. The flags given here will be used in the call to request_irq(). In UIO, the RX interrupt shares the same vector with other interrupts. With lsmod you can verify that device driver is loaded for particular hardware. An example will be given for managing an image rescaling T. that irq number is also in the proc/interrupts, maybe The generic interrupt handler of uio_pdrv_genirq will simply disable the interrupt line using disable_irq_nosync(). char *name: Required. The aim of this patch is to enable real time capabilities in the Linux kernel. Binding NIC drivers¶ As DPDK uses its own poll-mode drivers in userspace instead of traditional kernel drivers, the kernel needs to be told to use a different, pass-through style driver for the devices: VFIO (Virtual Functio I/O) or UIO (Userspace I/O). Logical CPU. struct uio_info 2. If you didn’t know about those examples, I suggest you check it out every time you start playing with a new IP core. The +uio_dummy module does this as it triggers the event mechanism in a timer How Do I Get Started Writing a Simple PCIe Driver for Linux I am working on development board for one of our FPGA designs prior to the arrival of actual hardware (and a driver from our customer). Other Apps. 825731] mmc0: Timeout waiting for hardware interrupt. Usable Simulink Embedded Coder Target for Linux Michal Sojka, Pavel Píša Czech Technical University in Prague Technická 2, 121 35 Praha 6, Czech Republic lib. x / 3. 6 Mar 2018 How do I expos the AXI bus at 0x43C00000 as uio devices? interrupts = <0x0 0xd 0x4 0x0 0xe 0x4 0x0 0xf 0x4 0x0 0x10 0x4 0x0 0x11 0x4  To support PCI style interrupts a minimal kernel module using the Linux UIO framework is In this example, the permissions of /resource0 are changed. I'm neither a software guy nor a Linux guy, so I can't really help with how to setup/build a driver, but hopefully you can find a good tutorial and follow the logic of the Microblaze driver. EDMA3 LLD is a component of the processor SDK RTOS. The host ARM interrupts the PRU by generating a system event that the PRU  17 Jan 2015 Research conducted using Linux as a sample code base found that . org/doc/html/v4. Scheduling cost. Signal eventfd. Using the Realtime Preemption Patch on ARM CPUs Jan Altenberg Linutronix GmbH Auf dem Berg 3, 88690 Uhldingen-Muehlhofen, Germany jan. For About the PRU Interrupt To Host Mechanism. The buttons are connected via axi_gpio (IOCarrierCard). Between the two, use VFIO if you can. If you are concerned more with configuration not performance the vmxnet3 driver can be set to interrupt mode in VPP. It only provides a way to interact with IPI as a device. Threaded ISR. **** Configure interrupt to detect rising edge. system. This module is intended to try to make the lives of input driver developers easier by allowing them to test various serio devices (mainly the various touchpads found on laptops) without having to have the physical device in front of them. For building the no-OS software, an example Makefile is also provided (Makefile. This can be done by adding the kv pair to the bootargs line in the uEnv. c. 15 User Space Application Interrupt Processing Example | 用户空间  27 Oct 2012 My question pertains to Linux UserIO (UIO) based user mode device driver And it won't help when/if I start trying to send interrupts to my app. It might be desirable to add an ioctl() call to the UIO driver which simply blocks until the interrupt count is at least 1 more than the last call, leaves the interrupt What is the difference between interrupt-driven I/O versus polling I/O?. of_id=generic-uio'" to uLinuxEnv. 259 * 260 * Interrupt sharing is not supported. Linux kernel. EDMA3 LLD has the following two modules: From: Magnus Damm <[hidden email]> This patch adds a "Unique IRQ Mode" to the uio_pdrv UIO platform driver. If you had no interrupt at all, you could set irq to UIO_IRQ_NONE, though this rarely makes sense. While the threads used by an DPDK application are pinned to logical cores on the system, it is possible for the Linux scheduler to run other tasks on those cores also. It is necessary to know how microcomputers work internally: memory addressing, interrupts, etc. Introduction¶. UIO is a step in that direction, but If you want to correctly handle interrupts in user-space then UIO might not be enough, for example if the device doesn't support the PCI-spec's interrupt disable bit which UIO relies on. This Linux kernel change "UIO: fix up the UIO documentation" is included in the Linux 2. If you want to add code to a Linux kernel, the most basic way to do that is to add some source files to the kernel source tree and recompile the kernel. example of doing interrupt? 10/10/linux-uio-gpio-interrupt/. Linux graphics course Pointer to the devices uio_device structure */ static irqreturn_t uio_interrupt (int irq, void * dev_id This article, which is part of the series on Linux device drivers, talks about the typical ioctl() implementation and usage in Linux. A driver similar to igb_uio is available in the kernel: uio_pci_generic. Now I want to synchronize the time of interrupt in the user space, i. It was written by Ingo Molnar. But instead of providing an API to setup an interrupt handler, it uses instead the realtime RTDM device file. xilinx. The driver already implements an irq_control() to make this possible, you must not implement your own. Enable IOMMU in Linux by adding intel_iommu=on to kernel parameters, for example, using GRUB (see /etc/grub/grub. / Documentation / DocBook / uio-howto. struct uio_info This structure tells the framework the details of your driver; Some of the members are required, others are optional. The device tree configured the pruss_uio driver to handle events 20 through 27, so the driver receives the interrupt and unblocks /dev/uio0, informing the host process of the PRU event. de Abstract During the last few years, Linux has established itself as the fastest growing platform in the embedded sector. Wakeup Latency. UIO frame work does this by letting the application kernel driver to map the hardware IO to the user space process. However Controlling GPIO from Linux User Space This application note explains how to drive GPIO outputs and read the state of GPIO inputs from the Linux user-space on the STM32F429. 6. For interrupt-driven data transfer to happen successfully, the hardware should be able to generate interrupts with the following semantics: For input, the device interrupts the processor when new data has arrived and is ready to be retrieved by the system processor. Ive been investigating the different options for interacting with the PL from the PS running Linux and have been having some issues with interrupts using userspace I/O (uio). void. Chapter 11 describes how you can use Qt in your BBB projects and Qt Creator is a tool that can greatly improve your programming experiences. c) – For more advanced users as a minimal kernel space driver is required to setup the UIO framework – This is the most universal and likely to handle all situations since the kernel space driver can be very custom This article is a continuation of the Series on Linux Device Driver, and carries on the discussion on character drivers and their implementation. Code Browser 2. These data types are used throughout USB, and in APIs including this host side API, gadget APIs, usb character devices and debugfs interfaces. I think that we just need a good example showing how PRU0 code writes to PRU0 DRAM and how ARM Linux code reads from PRU0 DRAM. UIO¶. The physical addresses of the regions are provided to userspace and the allocated memory is freed when the uio device is closed. I followed the Derekmolloy tutorial which is a great tutorial and helps a lot. UIO device name. Normally, FPGA register/interrupt control is done using a kernel module, which has direct access to physical memory and can register interrupt handlers. for DPDK. A comparison of the architecture Linux Industrial I/O Subsystem IIO Overview The Industrial I/O subsystem is intended to provide support for devices that in some sense are analog to digital or digital to analog converters (ADCs, DACs). The PRU_ARMtoPRU_Interrupt example you found is actually legacy code from before 2015 back when TI still supported using UIO with the PRU - the ARM and setup portions of that code disappeared somewhere along the line, so we have been talking about removing that code or at least commenting it so it's clear that example is no longer supported. g. User mode I/O was the norm from the first PC in 1982 until Windows 2000. Linux Kernel. com. Adding an interrupt handler Please have a look at uio_cif. Interrupt handler address¶ In order to find the interrupt handler address we first need to find the start address of the code segment where interrupt handler resides. This chapter describes the structure of a character device driver, focusing in particular on character driver entry points. The second case comes about when DMA is used asynchronously. • unsigned long irq_flags: Required if you’ve set irq to a hardware interrupt number. a. Generic PCI UIO driver Making the driver recognize the device Things to know about uio_pci_generic > I'm trying to make linux 3. How to avoid writing kernel drivers. The application source code we are using in this tutorial is one of the many valuable examples provided by Xilinx in the installation files. The interrupts from AXI and Fabric (PL-PS) are enabled. Who Should Attend – The course is designed for real-time engineers who are developing Embedded Linux BSPs and Device Drivers for Embedded Linux distributions. h) use a few legacy framework (interrupt handling, device file, and sysfs) e. 575 This prevents the device from generating further interrupts until the 576 bit is cleared. VFIO Virtual Function I/O* Derivative of UIO Enhanced interrupt support PCI config space virtualization IOMMU support – via UIOMMU Supports virtualization and userspace drivers Developed by Tom Lyon VFIO is a device driver * not limited to SR-IOV You need a special devicetree - take zynq-zc706-adv7511-ad9361-4-fmcomms2-3-4-userspace. tmpl blob Welcome to lxr. FIGURE   2017年11月1日 了解了UIO 驱动在Linux系统中的位置后,让我们对参考资料(Linux User . Any hardware device will only work if device driver is loaded. . Create an event or check for an existing event for which the system will wait. The Device Tree Blob(. Interrupt handler that has data pending to be read from corresponding descriptor ring should return IRQ_HANDLED. It's important to load your drivers at the kernel manual with the shell command: modprobe uio_pdrv_genirq. All devices have addresses through which they communicate with each other struct uio_info Adding an interrupt handler Using uio_pdrv for platform devices Using uio_pdrv_genirq for platform devices 4. It is always a good practice to monitor swap space usage in Linux to ensure that your system operates relative to its memory demands. The user space interrupt service routine also communicates directly with the UIO character device file but is not included with the driver functions since it is application dependent. This In the following example we create two representors on PF address 0000:05:00. First user will be virtualization where a qemu userspace process needs to give guest OS access to the device. Why Linux is not an RTOS Applications run in “user space” All hardware interaction is in “kernel space” All i/o via files and sockets Applications are processes Default scheduling policy is time shared POSIX API Is Linux real-time? ****Get Interrupt number for GPIO number (for SODIMM_101). I'm writting a driver for a synthesized device in an FPGA. We enable tickless Linux capability. How to write a UIO driver Example target device: SuperH on-chip timer unit (TMU) . Files that do not support seeking-for example, terminals-always read from the current position. He distinguished between: Level type In addition, devices that run LINUX on ARM have a set of LINUX drivers that control the EDMA. DPDK is licensed under the Open Source BSD License. Prior to VFIO, these drivers had to either go through the full development cycle to become proper upstream driver, be maintained out of tree, or make use of the UIO framework, which has no notion of IOMMU protection, limited interrupt support, and requires root privileges to access things like PCI configuration space. 4. A new user level driver framework for Linux Virtual Function I/O* Originally developed by Tom Lyon (Cisco) IOMMU-based DMA and interrupt isolation Full devices access (MMIO, I/O port, PCI config) Efficient interrupt mechanisms Modular IOMMU and device backends * not limited to SR-IOV Libmetal and OpenAMP for Zynq Devices 6 UG1186 (v2017. The Beaglebone Black PRU's can send interrupt style events to user mode host programs. com Chapter 1: Overview Prerequisites To use the OpenAMP Framework effectively, you must have a basic understanding of: • Linux, PetaLinux, and Xilinx SDK. This change is authored by Hans J Koch <hjk [at] linutronix. 0. If you don't have a hardware generated interrupt but +want to trigger the interrupt handler in some other way, set +<varname>irq</varname> to <varname>UIO_IRQ_CUSTOM</varname>. virtualDev = “e1000” to ethernet1. Introduction. In this practical, example-driven book, one of the world's most experienced Linux driver developers systematically demonstrates how to develop reliable Linux Device Tree アクセス関数まとめ (Linux Kernel) Device Tree 入門; LinuxCon Japan 2014; sed で遊ぶ; U-Boot と Linux Kernel のメインラインで Zynq を動かす 2014年4月版; 2月 (1) 1月 (4) 2013 (29) 12月 (3) 10月 (1) 9月 (2) 7月 (1) I will just take this opportunity to once again poke you in the direction of UIO; there have been patches to the kernel I've seen fly by lately which aim to limit the address space that /dev/mem can actually map. h . We demonstrate how As the title says, this tutorial explains how I did in order to be able to use the AXI DMA inside the embedded Linux on a Zybo board. The UIO framework defines a small kernel-space component that performs two key tasks: a. The IPC example is located at C:\ti\ipc_3_43_02_04\examples\DRA7XX_linux_elf\ex02_messageq. The interrupts were not working for me, so I used polling. User-Level. dtb file into a human readable . there is an irq number and the second nome is an integer refering to how it is triggered. The following paragraphs explain the different sections of this file. Koch Linutronix GmbH Bahnhofstr. Memory Access and Interrupt Handling through UIO. It's been rewritten from the last time patches were posted to lkml and is much simpler. The original implementation of interrupt handling in Linux uses the __do_IRQ() super-handler, which is able to deal with every type of interrupt logic. Is there a way to send an interrupt (one of the 64 system interrupt events documented in the PRU-ICSS literature) from userspace? GPIO, SPI and I2C from Userspace, the True Linux Way Baruch Siach baruch@tkos. The most recent patches and enhancements are available for download. > > VFIO is a better choice if IOMMU is available, but often userspace Elixir Cross Referencer. The diagrams in slides 6, 7, 8, 11, and 12 are by Wikipedia, and are licensed under the Creative Commons Attribution-Share Alike 3. Implementing hardware abstraction via "hardware operations" data structures is typical in the Linux kernel. To view each device attached to your system as well as its mount point, you can use the df command (checks Linux disk space utilization) as shown in the image below: Configure sudo for users and groups under /etc/sudoers. 4 and Petalinux 2015. Hi, I have implemented a simple UIO driver for AXI GPIO to be run on Zynq platform. Interrupt Latency. Contribute to spotify/linux development by creating an account on GitHub. + - reg : address range(s) of the device (up to MAX_UIO_MAPS) + - interrupts : interrupt of the device + +Example: + c64fpga at  22 May 2017 GPIO Interrupts I have the JetsonHacks GPIO interface example you could refer to gpio header, $TOP/kernel/include/linux/gpio. I'm one of FPGA designers on the project and I have no experience writing a PCI or PCIe driver. T. No Interrupt support for NXSB-PCA and NX-PCA-PCI boards On big-endian machines the user is responsible for converting send/receive packets from/to little endian. They works in uio in petalinux. In fact, a tiny (150 lines in the sample driver, including comments etc) kernel-side driver to handle some basic interrupt routine is needed as part of every UIO driver. It's expected that more features of interest to virtualization will be added to this driver in the future. User mode apps can and do interact with I/O devices today. no LXR (formerly "the Linux Cross Referencer") is a software toolset for indexing and presenting source code repositories. SW Workshop #2 – Introduction to Linux on Altera SoC. Then I change the uio irq handler in the uio_pdrv_genirq. code of lsuio can serve as an example for getting information about an UIO device. We will start by generating a new application called "gpio-uio-test". 2. virtualDev = “vmxnet3” Save the file and power on the VM. This interrupt simulation is done by calling uio_event_notify() from the timer's event handler. Creating an UIO driver. The PRU_SW Project contains example code demonstrating basic tasks executed by the PRU Subsystem. Preempt the running task and schedule the DPDK app to run. A1, which works) I want it to run a loop on the PRU so that it loads 4096 samples into a memory block which can be read from Linux space. The RT-Preempt patch allows user space programs to run in real-time [2], [3]. Implication: When insmod igb_uio and running l3fwd-power APP, link status getting doesn’t work properly. c and uio_driver. Now we will see Interrupts Example Program in Linux Kernel. Hardware. So here, we will be using the “power-save” mode from the above table, and use a pin-change interrupt to wake up from this sleep mode. After logging in to the Linux, try the gpio-dev-mem-test command to directly access the GPIO devices. I2C is a multi-master synchronous serial communication protocol for devices. Microprocessor programming. This prevents the device from generating further interrupts until the bit is cleared. In a previous post about an Ambient Light sensor using an Op-Amp Comparator, I mentioned that we would be using the op-amp output to “wake up” an ATmega168. You will have to use "dmem-uio". The next step is to write a program for the PRU cpu and start it from the ARM cpu running Linux. With a kernel module, only 1 system call per interrupt would be  10 Oct 2014 The Linux kernel provides a userspace IO subsystem (UIO) which enables Example. I made the following vivado project attached as image. The PCI bus implementation for Linux uses the Userspace IO kernel API to access the bus. New training. This will provide the start address kept in the ‘base’ field. Some time ago I worked on a project on Beaglebone Black that had to control some IOs, UART ports, also had to take some decisions Read about 'AXI GPIO Interrupt' on element14. Zybo - AXI DMA Inside Embedded Linux: As the title says, this tutorial explains The generic-uio part is required for our peripherals to be recognized and will be explained later on. Introduction to Multimedia Support Introduction In the last three years, Renesas has been working hard to apply it's Open Source community participation standards that have been successfully adopted in the Linux Kernel space to User Space applications. To copy files into your CCS project, you can simply select the files you want in Windows explorer then drag and drop them into your project in CCS. 5. if you convert your device tree blob . Skaali, Department of Physics, University of Oslo FYS 4220/9220 - 2011 - Lecture #7 9 The Linux ”Completely Fair Scheduler” • The Completely Fair Scheduler (CFS) was merged into the 2. h> and takes care of everything that may change across different Alpha-based computers. option is Userspace I/O https://www. I see many UIO examples, but not examples using the pruss or pru_rproc modules that we have running. NIC. It also includes full documentation and two example drivers and two example userspace programs that test those drivers. 3. The interrupt handler gets the input data, acknowledges the interrupt, and awakens the process, which is now able to read data. In this column, the author takes the reader through the process of writing I2C clients in Linux. Demonstration Module 1 - the most basic module example. • How to boot a Xilinx board using JTAG boot. We then show how it is possible to talk to these peripherals using −The Linux UIO framework allows USDPAA threads to wait for interrupts from software portals by doing file operations like select(fd) on the user space device − USDPAA threads will dequeue and process frames from portals after a data available {"serverDuration": 36, "requestCorrelationId": "002335c530d47396"} Confluence {"serverDuration": 31, "requestCorrelationId": "003c0e3ae365e0e2"} 573 574 On each interrupt, uio_pci_generic sets the Interrupt Disable bit. The following example does not use the IPI shared buffer. to notify application (C/C++ code) when external interrupt happens and being handled in the kernel space. EAL in a Linux-userland Execution Environment¶ In a Linux user space environment, the DPDK application runs as a user-space application using the pthread library. – IPI device, e. edging the interrupt. Bastin UCL/CESAME (Belgium) USENIX’05 / Freenix track Anaheim, USA, June 10-15, 2005 Designed to run on x86, POWER and ARM processors, it runs mostly in Linux userland, with a FreeBSD port available for a subset of DPDK features. UIO provides generic ways of handling IRQ in kernel space as a driver . François. It just requires some sophistication and a small proxying layer in the kernel. Most user space drivers are polling based as interrupt handling is done only in supervisor (i. For example, suppose there is space for 20 bytes more in a file before reaching a limit. of Informatics at the University of Oslo, Norway. For example, Figure 11-9 in the book illustrates Qt Creator in action for the creation of the Temperature Sensor application user interface. 1 Generator usage only We route only one interrupt to that core. 12/driver-api/uio-howto. UIO drivers are a convenient method to Device tree compiler and its source code located at scripts/dtc/. This ways linux. kernel) mode. I try to use "GPIO8_ALS_PROX_INT" (on developer kit J21, pin 37) as an external interrupt. the interrupt handler in some other way, set irq to UIO_IRQ_CUSTOM. Preempt) is a enhancement to the Linux kernel. In <linux/usb/ch9. cifX Device Driver | Linux (Kernel 2. The Linux kernel is a free and open-source, monolithic, Unix-like operating system kernel. – UIO driver for SH  7 Sep 2017 We will go through an example on a zynq platform and a programmable logic that raises an interrupt after filling some memory area with a  This HOWTO describes concept and usage of Linux kernel's Userspace I/O to handle an interrupt and provide access to the memory space of the device. Can you recommend one? Thanks, Mark J UIO drivers are made of two parts: a small kernel module that registers the driver and contains a basic interrupt handler, and an userspace part, which is the core of the driver. c in the Xilinx Linux git tree, only uio_pdrv_genirq can work out of the box with device tree configuration. One important example is the struct alpha_machine_vector data structure. Device Driver uio_core uio_dev. Documentation http://alvarom. [$ 8. I It is used in the Linux multimedia architecture for SH-Mobile, a system-on-chip with video compression and image manipulation functions. 0 Unported license It also adds a polling and interrupt mode switch control example. If mmap() at user-space handles this, that works for us. Thanks! -----> This adds a generic uio driver that can bind to any PCI device. While RTOS can directly access memory locations, e. User space is responsible: 257 * for performing hardware specific acknowledge and re-enabling of: 258 * the interrupt in the interrupt controller. Preemption may be disabled when the CPU is handling an USB-Standard Types¶. UIO frame work allows user space applications to own the device. Introduction to Linux Loadable Kernel Modules. 0 or later. This command will turn on all four LEDs on the board. Device tree interrupt assignments are a little wonky. So, for example, a pointer “kp” to a struct kobject embedded within a struct uio_map could be converted to a pointer to the containing uio_map structure with: TRex Advanced Stateful (ASTF) mode supports a user space TCP stack for emulating L7 protocols such as HTTP for router firewall testing. 3). The board used is Zedboard. In this series of articles I describe how you can write a Linux loadable kernel module (LKM) for an embedded Linux device. Problem is I haven't done any assembler for 40 years, so I'm a bit rusty. The interrupt status of the Red Rapids device can be monitored with a read() call to the assigned UIO device. so. In the guest, bind the virtio device to the uio_pci_generic kernel module and start the forwarding application. 1. I'm running into a difficulty with the Modular SGDMA that is used in the HPS Memory example. h> you will find the USB data types defined in chapter 9 of the USB specification. dtc file, look for the amba pl category and your gpio device in the interrupt sections. An example of how to use Avalon interrupts on the Cyclone V FPGA - zhemao/interrupt_example Spotify's Linux kernel for Debian-based systems. The DMA package includes a specific device driver that fully compiles into most distributions of the operating system although the vendors will provide a cut-down small version of Linux known as uC-Linux. 25, 88690 Uhldingen, Germany hjk@linutronix. Linux (and most non-RT OS's) doesn't really provide a direct way to do this. support these bits. After doing its work, userspace can reenable the interrupt by writing 0x00000001 to the UIO device file. net is a reader-supported news site dedicated to producing the best coverage from within the Linux and free software development communities. uio-test-system. 23 release of the Linux kernel. linux). Chapter 10 Drivers for Character Devices. Using Linux Core Isolation to Reduce Context Switches. • ISR Interrupt Service Routine • Rxx Any Revision Number • UIO User (space) I/O 1. PS: I used the url Handling GPIO interrupts in userspace on Linux with UIO · /var/log/andrey For each other, here is my hardware, the device tree and the code for a axi gpio interrupt. sudo pillar map to actual sudo attributes: 11 Dec 2006 Hardware that is ideally suited for an UIO driver fulfills all of the following: Now the userspace part can determine the cause of the interrupt, but it cannot re- enable interrupts. Userspace drivers • Writing kernel device drivers can be difficult • Luckily, there are generic drivers that that allow you to write most of the code in userspace • We will look at three Hi, I am working on an embedded Linux project. kernel. 1 thought on “ How to Design and Access a Memory-Mapped Device in Programmable Logic from Linaro Ubuntu Linux on Xilinx Zynq on the ZedBoard, Without Writing a Device Driver – Part One ” Marc D June 3, 2014 at 1:29 am Unfortunately, it doesn't seem to have interrupt support. Userspace input output or UIO Enables writing hardware drivers in user space with a small kernel module providing memory space mapping and interrupt support. co. 5 Interrupt Service Code – Hardware interrupt handling is of key significance in real-time systems, because it is usually through interrupts that the system is informed of external events. How to implement an interrupt driven GPIO input in Linux Posted by Cliff Brake 2009-01-10 2009-01-13 8 Comments on How to implement an interrupt driven GPIO input in Linux With Linux, some of the things that seem like they should be easy are not — at least at first glance. For example, igb_uio supports all interrupt types (legacy, MSI, and MSI-X), while uio_pci_generic only supports legacy interrupts. I would like to present here a simple solution to write an interrupt driven user space application with the help of the generic user IO kernel driver. When using the PRU UIO interface we need a user program to load and start the PRU application and we need a PRU executable binary. 1 Generator usage only permitted with license. Devices needing only memory mapped I/O access do not require a kernel driver. This provides all the definitions needed. LXR was initially targeted at the Linux source code, but has proved usable for a wide range of software projects. includes interrupt management (using User Space I/O (UIO) as back. The RTDM driver in kernel space does the the first, most critical part of the interrupt handling which must be carefully done to prevent system crashes. I2C is a protocol for communication between devices. of_id="generic-uio" Furthermore it's important to configure and enable the interrupts at your code. SW Workshop #3 . This happens, for example, with data acquisition devices that go on pushing data even if nobody is reading them. Helper library for writing linux user-space drivers with UIO. Difference is in which address space the drivers run. de> on Mon Nov 26 22:03:29 2007 +0100. cpp; for further information have a look at the paper Userspace I/O drivers in a realtime context; Configure your own display Running virtualized native drivers in User Mode Linux V. Some in-depth knowledge of C programming is needed, like pointer usage, bit manipulating functions, etc. uio_pci_generic detects this support, and won't bind to: devices which do not support the Interrupt Disable Bit in the command register. It works pretty much the same way as igb_uio, except that it is more limited in what it can do. UIO is not a try to migrate all the Linux kernel drivers to userspace. Writing a driver in userspace Getting information about your UIO device mmap() device memory Waiting for interrupts 5. Resolution/Workaround: compared to Linux’ and iptables, ipset, and the newer nftables. TRex saves memory when generating traffic by using APIs with a pull approach rather than push, and utilizing DPDK for batching the packets. The software stack consists of two main sections: the user space driver and low level kernel driver. example", the _only_ thing it can possibly Does anyone have a working linux device driver that works for interrupt of custom ip-cores? The AR 51138 shows an example ip-core that contains an own interrupt controller that supports multiple interrupt sources and registers into the global interrupt controller of the Zynq. The API that is used to control GPIO is the standard Linux GPIOLIB interface. Run the ISR thread. It will enable your card to be seen and read and written to presumably, but as for whether it is possible to use it with Linuxcnc, that is another question. This is continuation post to our earlier kernel panic reference post ( Redhat Enterprise Linux 6 – Kernel Panic and System Crash – Troubleshooting Quick Reference ) where we have discussed several types of kernel panic issues and their reasons. Replied by ArcEye on topic Add kernel-modul uio_netx OK - Well done you have managed to compile the kernel module and load it. 嵌入式 Linux 知识库 (elinux. This is the first such API released on Linux to address a number of important problems, including: Linux Kernel and UIO frame work call the interrupt handler one by one in sequence. It is possible, if inelegant, to use that driver with a device that does not issue interrupts. The Device Driver Environment (DDE) is a wrapper library that maps the interface expected by in-kernel Linux device drivers to the device driver interface provided by a certain host system. It means that the device should have capability to check the pending data without reading it out. Because of UIO only support one interrupt, so these two kinds of interrupt need to share one, and the receiving interrupt have the higher priority, so can’t get the right link status. For example, to make GPIO60 interrupt on a falling edge:. It is a tough reference. Using a server running VMware’s ESXi hypervisor, we set up a network of VMs consisting of a client and a target running Ubuntu and firewalls running Ubuntu Server, IncludeOS and Alpine Linux. UIO will be much more future-proof and the entire driver will be well under 100 lines without an interrupt. Most input and output devices are much slower than the CPU—so much slower that it would be a terrible waste of the CPU to make it wait for the input devices. This page describes each example and illustrates the interaction between the ARM, PRU, peripherals, and memory. I use uio to link the four gpio pins in my devicetree. Although dedicated UIO kernel drivers can be written, we are using a generic driver named uio_pdrv_genirq. We use only the Linux UIO (user mode driver) interface to handle and synchronize this interrupt with its associated user-mode application process. Unsolved Userspace I/O drivers in a realtime context Hans J. It aims to maximize overall CPU utilization while maximizing interactive performance. A high-level sensitive interrupt is triggered for the processor in event of incoming data on the peripheral. Guffens, G. I can see in my linux /proc/ interrupts. The interrupt starts masked and the user must explicitly  12 Mar 2017 Make life easy for yourself by using the Userpace IO (UIO) framework to Kernel interrupt handler • Usually very simple • For example, disable  17 Apr 2008 interact with a userspace process to process interrupts and control memory What UIO provides. For example, when you press a key on your keyboard it sends a signal to the processor via an IRQ channel (usually IRQ1) to let it know that it needs to process some data. See the LWN FAQ for more information, and please consider subscribing to gain full access and support our activities. In the _init function, which is called either upon module load or when booting the kernel, it grabs the required resources (it should also check for the presence of the device). Now we want to copy configuration and source files from the ex02_messageq IPC example into our project. 1-rc2 Powered by Code Browser 2. 10 Jan 2012 PRU Linux-based Example Code Build the UIO kernel driver. JPG. For example, if it is ethernet1, then change the line ethernet1. This solution will use spidev for controlling the AD9361 and uio for accessing the PL cores. The exact number will depend on the specific product and revision of the code. The most useful example of this is a memory-mapped device, but you can also do this with devices in I/O space (devices accessed with inb() and outb(), etc. To support PCI style interrupts a minimal kernel module using the Linux UIO framework is required. This prevents the device from generating further interrupts: until the bit is cleared. 1 Nov 2018 This example uses 3 system calls per interrupt due to limitations in generic-uio. I read about using UIO to get kernel interrupt from user-space. conf). This means that you have to permit your normal Linux user account to write to the edge file or setup the interrupts on the GPIO files by sshing into the BeagleBone Black as root. html. com/2014/12/17/linux-user-space-drivers-with- interrupts/  6 May 2016 interrupts = <0 57 0>; However, there is still no UIO device appearing (kernel log is silent on this matter). Such detail is not repeated in this article. This tutorial was written with Xilinx' Zynq-7000 EPP device in mind (an ARM Cortex-A9 combined with FPGA), but the general concepts apply for any Linux kernel using the device tree. h> 04 for example gives you the file descriptor required for this. PCI information about devices and address space is discovered through the /sys kernel interface and through a module called igb_uio. −The Linux UIO framework allows USDPAA threads to wait for interrupts from software portals by doing file operations like select(fd) on the user space device − USDPAA threads will dequeue and process frames from portals after a data available Replied by ArcEye on topic Add kernel-modul uio_netx OK - Well done you have managed to compile the kernel module and load it. 4. This event manifests itself by the presence of 4 readable data bytes on one of the /dev/uio[0:7] files. 8 run on a Beaglebone, but I'm facing problems > with high interrupt latency when using GPIO as interrupt source. The main advan-tage of this approach is that the most of the develop-ment happens in user-space, thus during prototyping The latter part of the course covers Embedded Linux Device Driver development including key device driver decisions and deployment considerations for Embedded Linux BSPs. Finally, the interrupts. What ties these various technologies together is that they are Userspace techniques for implementing functionality that previously required kernel-mode programming. 6. de Abstract Userspace I/O (UIO) drivers and realtime kernels often meet each other, since both are frequently used on and I add config CONFIG_UIO=y CONFIG_UIO_PDRV_GENIRQ=y in my kernel. The API is similar to the igb_uio driver used by the DPDK. In some cases vendors will to a signal that support external interrupts as a GPIO line as well. 261 */ 262: 263: uioinfo->handler = uio An example of interrupt-driven output is the implementation of /dev/shortint. 2 Tape Archive (TAR-806-91x-Rxx) The Linux device drivers are distributed on Red Rapids tape archive number TAR-806-910-Rxx. Register for device interrupts and provide interrupt indication to user space. Can you help me please. PCM-UIO96B-G Description. The web server in above example makes use of an in-kernel network . txt file in the BOOT partition. Hi all, In my current project we have to use the Linux SocketCAN layer to get on the bus, so I'm investigating existing resources and documentation for the In order to develop Linux device drivers, it is necessary to have an understanding of the following: C programming. Several other tutorials exist in order to install Linux on the Zybo platform (see references in the end of tutorial), so I won't cover that with much detail. android / kernel / tegra / c64768a7d671bcde80bca2aed93f9e07edc069c3 / . Resources for Linux SocketCAN. 16 – Change arguments of interrupt handler – Replace device_create() and device_destroy() invocations with appropriate code. altenberg@linutronix. If In the meantime, I’ve pasted below an example I’m working on in the hope it can be of use to you - just remember it is a work in progress. Every interrupt can be shared between di erent devices. DPDK App. im8mq-evk 支持jailhouse虚拟机,但是在实际测试中,gic测试和uio_ivshmem测试都很正常;测试linux时候,总是报: Page pool usage after cell creation: mem 69/993, remap 336/131072 [ 1771. UIO_MEM_PHYS indicates that addr is a physical address, generally for an I/O memory area. After an interrupt, the interrupts have to reenable. PC/104 digital I/O module with 96 bidirectional lines (GPIO), 48 of which support event sense interrupts. p file (from Molloy's example 13. Afterwards i was able to export it as UIO and Quick and Easy Device Drivers for Embedded Linux Using UIO Overview • Conventional Linux drivers • The UIO framework • An example UIO driver • Scheduling that info is taken from the device tree where vivado puts the correct info as you set it up. If an interrupt occurs, the operating system calls every interrupt handler registered for that particular interrupt line until the interrupt is served and the line is released. txt; Example for a UIO userspace driver: uio_access. In particular, Renesas has supported the Locate the line for the interface which you want to modify. The default permissions on the exported GPIO pins, for example the /sys/class/gpio/gpio72 directory, permit everybody to read the pin but only root to write to the files. Conventional PCI includes four interrupt lines. Applications interacted with I/O devices through device drivers running in user mode (ring 3 on x86). The code for the following examples is here pru-code. Then my Linux app would open /dev/uio0 (for example), mmap a view on it. In addition, this chapter covers the use of physio(9F) (in read(9E) and write(9E)) and aphysio(9F) (in aread(9E) and awrite(9E)) in the context of synchronous and asynchronous I/O Three tips to save time and effort by writing userspace device drivers to interface with hardware using GPIO, PWM and i2c If a write() requests that more bytes be written than there is room for (for example, the process' file size limit or the physical end of a medium), only as many bytes as there is room for shall be written. I am using Vivado 2015. zynq Dear Experts I need help regarding interrupt handling using UIO. 3) January 4, 2018 www. small code (820 lines in uio. It provides an overview of the API structure, and shows how that fits into a system development project. - uio_info  uio 0. In the project, I wish to get a GPIO interrupt in my user-space program. On Mon 2013-04-01 16:23:36, Pavel Machek wrote: > Hi! > > I'd like to get uio device tree bindings to work -- with recent FPGA > parts it will be important. Of the various UIO drivers in linux/drivers/uio/*. User-space device drivers. What the example does¶ First it has to include the <linux/input. Ensure SR-IOV is enabled on the system. Link the event created in step 4 with System Interrupt obtained in step 5. org) CE Linux Forum; Embedded Linux Wiki; Proejct Introduction Howto Build and Tips Sign in. c) with a feature that makes > it possible to via sysfs configure which GPIO-pin(s) that should generate > interrupt. It permits sharing a part of the memory to the user space and catch a given interrupt without the need of programming a … Help with Linux UIO based driver a. The kernel module is based on the generic uio module and is responsible for cifX hardware detection and preparation to allow mapping the device memory (DPM) to user space. If you don't care about frills, this may be a good candidate for UIO. In this section we will create an UIO driver using the enhanced generic UIO framework. Best Regards . I have a BBB, with Linux version 3. How do I display the list of loaded Linux Kernel modules or device drivers on Linux operating systems? This is an important task. linux uio interrupt example

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