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258 lines
7.4 KiB
258 lines
7.4 KiB
/** |
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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 <[email protected]> |
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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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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 <[email protected]>");
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