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Add /dev/gpiomem device for rootless user GPIO access
Signed-off-by: Luke Wren <luke@raspberrypi.org> bcm2835-gpiomem: Fix for ARCH_BCM2835 builds Build on ARCH_BCM2835, and fail to probe if no IO resource. See: https://github.com/raspberrypi/linux/issues/1154
This commit is contained in:
Luke Wren
popcornmix
@@ -32,3 +32,12 @@ config BCM_VC_SM
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help
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help
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Support for the VC shared memory on the Broadcom reference
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Support for the VC shared memory on the Broadcom reference
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design. Uses the VCHIQ stack.
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design. Uses the VCHIQ stack.
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config BCM2835_DEVGPIOMEM
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tristate "/dev/gpiomem rootless GPIO access via mmap() on the BCM2835"
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default m
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help
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Provides users with root-free access to the GPIO registers
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on the 2835. Calling mmap(/dev/gpiomem) will map the GPIO
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register page to the user's pointer.
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@@ -1,3 +1,6 @@
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obj-$(CONFIG_BCM_VC_CMA) += vc_cma/
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obj-$(CONFIG_BCM_VC_CMA) += vc_cma/
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obj-$(CONFIG_BCM2708_VCMEM) += vc_mem.o
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obj-$(CONFIG_BCM2708_VCMEM) += vc_mem.o
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obj-$(CONFIG_BCM_VC_SM) += vc_sm/
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obj-$(CONFIG_BCM_VC_SM) += vc_sm/
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obj-$(CONFIG_BCM2835_DEVGPIOMEM)+= bcm2835-gpiomem.o
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260
drivers/char/broadcom/bcm2835-gpiomem.c
Normal file
260
drivers/char/broadcom/bcm2835-gpiomem.c
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@@ -0,0 +1,260 @@
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/**
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* GPIO memory device driver
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*
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* Creates a chardev /dev/gpiomem which will provide user access to
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* the BCM2835's GPIO registers when it is mmap()'d.
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* No longer need root for user GPIO access, but without relaxing permissions
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* on /dev/mem.
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*
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* Written by Luke Wren <luke@raspberrypi.org>
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* Copyright (c) 2015, Raspberry Pi (Trading) Ltd.
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*
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that the following conditions
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* are met:
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* 1. Redistributions of source code must retain the above copyright
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* notice, this list of conditions, and the following disclaimer,
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* without modification.
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* 2. Redistributions in binary form must reproduce the above copyright
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* notice, this list of conditions and the following disclaimer in the
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* documentation and/or other materials provided with the distribution.
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* 3. The names of the above-listed copyright holders may not be used
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* to endorse or promote products derived from this software without
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* specific prior written permission.
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*
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* ALTERNATIVELY, this software may be distributed under the terms of the
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* GNU General Public License ("GPL") version 2, as published by the Free
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* Software Foundation.
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*
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* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS
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* IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO,
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* THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
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* PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR
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* CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
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* EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
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* PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
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* PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF
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* LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
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* NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
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* SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
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*/
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#include <linux/kernel.h>
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#include <linux/module.h>
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#include <linux/of.h>
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#include <linux/platform_device.h>
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#include <linux/mm.h>
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#include <linux/slab.h>
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#include <linux/cdev.h>
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#include <linux/pagemap.h>
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#include <linux/io.h>
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#define DEVICE_NAME "bcm2835-gpiomem"
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#define DRIVER_NAME "gpiomem-bcm2835"
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#define DEVICE_MINOR 0
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struct bcm2835_gpiomem_instance {
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unsigned long gpio_regs_phys;
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struct device *dev;
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};
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static struct cdev bcm2835_gpiomem_cdev;
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static dev_t bcm2835_gpiomem_devid;
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static struct class *bcm2835_gpiomem_class;
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static struct device *bcm2835_gpiomem_dev;
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static struct bcm2835_gpiomem_instance *inst;
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/****************************************************************************
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*
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* GPIO mem chardev file ops
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*
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***************************************************************************/
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static int bcm2835_gpiomem_open(struct inode *inode, struct file *file)
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{
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int dev = iminor(inode);
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int ret = 0;
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dev_info(inst->dev, "gpiomem device opened.");
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if (dev != DEVICE_MINOR) {
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dev_err(inst->dev, "Unknown minor device: %d", dev);
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ret = -ENXIO;
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}
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return ret;
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}
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static int bcm2835_gpiomem_release(struct inode *inode, struct file *file)
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{
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int dev = iminor(inode);
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int ret = 0;
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if (dev != DEVICE_MINOR) {
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dev_err(inst->dev, "Unknown minor device %d", dev);
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ret = -ENXIO;
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}
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return ret;
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}
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static const struct vm_operations_struct bcm2835_gpiomem_vm_ops = {
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#ifdef CONFIG_HAVE_IOREMAP_PROT
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.access = generic_access_phys
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#endif
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};
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static int bcm2835_gpiomem_mmap(struct file *file, struct vm_area_struct *vma)
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{
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/* Ignore what the user says - they're getting the GPIO regs
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whether they like it or not! */
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unsigned long gpio_page = inst->gpio_regs_phys >> PAGE_SHIFT;
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vma->vm_page_prot = phys_mem_access_prot(file, gpio_page,
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PAGE_SIZE,
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vma->vm_page_prot);
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vma->vm_ops = &bcm2835_gpiomem_vm_ops;
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if (remap_pfn_range(vma, vma->vm_start,
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gpio_page,
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PAGE_SIZE,
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vma->vm_page_prot)) {
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return -EAGAIN;
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}
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return 0;
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}
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static const struct file_operations
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bcm2835_gpiomem_fops = {
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.owner = THIS_MODULE,
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.open = bcm2835_gpiomem_open,
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.release = bcm2835_gpiomem_release,
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.mmap = bcm2835_gpiomem_mmap,
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};
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/****************************************************************************
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*
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* Probe and remove functions
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*
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***************************************************************************/
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static int bcm2835_gpiomem_probe(struct platform_device *pdev)
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{
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int err;
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void *ptr_err;
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struct device *dev = &pdev->dev;
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struct resource *ioresource;
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/* Allocate buffers and instance data */
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inst = kzalloc(sizeof(struct bcm2835_gpiomem_instance), GFP_KERNEL);
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if (!inst) {
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err = -ENOMEM;
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goto failed_inst_alloc;
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}
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inst->dev = dev;
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ioresource = platform_get_resource(pdev, IORESOURCE_MEM, 0);
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if (ioresource) {
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inst->gpio_regs_phys = ioresource->start;
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} else {
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dev_err(inst->dev, "failed to get IO resource");
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err = -ENOENT;
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goto failed_get_resource;
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}
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/* Create character device entries */
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err = alloc_chrdev_region(&bcm2835_gpiomem_devid,
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DEVICE_MINOR, 1, DEVICE_NAME);
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if (err != 0) {
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dev_err(inst->dev, "unable to allocate device number");
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goto failed_alloc_chrdev;
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}
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cdev_init(&bcm2835_gpiomem_cdev, &bcm2835_gpiomem_fops);
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bcm2835_gpiomem_cdev.owner = THIS_MODULE;
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err = cdev_add(&bcm2835_gpiomem_cdev, bcm2835_gpiomem_devid, 1);
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if (err != 0) {
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dev_err(inst->dev, "unable to register device");
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goto failed_cdev_add;
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}
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/* Create sysfs entries */
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bcm2835_gpiomem_class = class_create(THIS_MODULE, DEVICE_NAME);
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ptr_err = bcm2835_gpiomem_class;
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if (IS_ERR(ptr_err))
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goto failed_class_create;
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bcm2835_gpiomem_dev = device_create(bcm2835_gpiomem_class, NULL,
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bcm2835_gpiomem_devid, NULL,
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"gpiomem");
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ptr_err = bcm2835_gpiomem_dev;
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if (IS_ERR(ptr_err))
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goto failed_device_create;
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dev_info(inst->dev, "Initialised: Registers at 0x%08lx",
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inst->gpio_regs_phys);
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return 0;
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failed_device_create:
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class_destroy(bcm2835_gpiomem_class);
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failed_class_create:
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cdev_del(&bcm2835_gpiomem_cdev);
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err = PTR_ERR(ptr_err);
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failed_cdev_add:
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unregister_chrdev_region(bcm2835_gpiomem_devid, 1);
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failed_alloc_chrdev:
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failed_get_resource:
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kfree(inst);
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failed_inst_alloc:
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dev_err(inst->dev, "could not load bcm2835_gpiomem");
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return err;
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}
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static int bcm2835_gpiomem_remove(struct platform_device *pdev)
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{
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struct device *dev = inst->dev;
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kfree(inst);
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device_destroy(bcm2835_gpiomem_class, bcm2835_gpiomem_devid);
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class_destroy(bcm2835_gpiomem_class);
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cdev_del(&bcm2835_gpiomem_cdev);
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unregister_chrdev_region(bcm2835_gpiomem_devid, 1);
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dev_info(dev, "GPIO mem driver removed - OK");
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return 0;
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}
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/****************************************************************************
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*
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* Register the driver with device tree
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*
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***************************************************************************/
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static const struct of_device_id bcm2835_gpiomem_of_match[] = {
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{.compatible = "brcm,bcm2835-gpiomem",},
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{ /* sentinel */ },
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};
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MODULE_DEVICE_TABLE(of, bcm2835_gpiomem_of_match);
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static struct platform_driver bcm2835_gpiomem_driver = {
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.probe = bcm2835_gpiomem_probe,
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.remove = bcm2835_gpiomem_remove,
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.driver = {
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.name = DRIVER_NAME,
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.owner = THIS_MODULE,
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.of_match_table = bcm2835_gpiomem_of_match,
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},
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};
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module_platform_driver(bcm2835_gpiomem_driver);
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MODULE_ALIAS("platform:gpiomem-bcm2835");
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MODULE_LICENSE("GPL");
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MODULE_DESCRIPTION("gpiomem driver for accessing GPIO from userspace");
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MODULE_AUTHOR("Luke Wren <luke@raspberrypi.org>");
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