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   1 From 13d6f1d6ccff0a381bd1e8149b4964158627d5cc Mon Sep 17 00:00:00 2001
   2 From: Luke Wren <luke@raspberrypi.org>
   3 Date: Fri, 21 Aug 2015 23:14:48 +0100
   4 Subject: [PATCH] Add /dev/gpiomem device for rootless user GPIO access
   5
   6 Signed-off-by: Luke Wren <luke@raspberrypi.org>
   7
   8 bcm2835-gpiomem: Fix for ARCH_BCM2835 builds
   9
  10 Build on ARCH_BCM2835, and fail to probe if no IO resource.
  11
  12 See: https://github.com/raspberrypi/linux/issues/1154
  13 ---
  14  drivers/char/broadcom/Kconfig           |   8 +
  15  drivers/char/broadcom/Makefile          |   1 +
  16  drivers/char/broadcom/bcm2835-gpiomem.c | 258 ++++++++++++++++++++++++
  17  3 files changed, 267 insertions(+)
  18  create mode 100644 drivers/char/broadcom/bcm2835-gpiomem.c
  19
  20 --- a/drivers/char/broadcom/Kconfig
  21 +++ b/drivers/char/broadcom/Kconfig
  22 @@ -16,3 +16,11 @@ config BCM2708_VCMEM
  23            Helper for videocore memory access and total size allocation.
  24
  25  endif
  26 +
  27 +config BCM2835_DEVGPIOMEM
  28 +       tristate "/dev/gpiomem rootless GPIO access via mmap() on the BCM2835"
  29 +       default m
  30 +       help
  31 +               Provides users with root-free access to the GPIO registers
  32 +               on the 2835. Calling mmap(/dev/gpiomem) will map the GPIO
  33 +               register page to the user's pointer.
  34 --- a/drivers/char/broadcom/Makefile
  35 +++ b/drivers/char/broadcom/Makefile
  36 @@ -1 +1,2 @@
  37  obj-$(CONFIG_BCM2708_VCMEM)    += vc_mem.o
  38 +obj-$(CONFIG_BCM2835_DEVGPIOMEM)+= bcm2835-gpiomem.o
  39 --- /dev/null
  40 +++ b/drivers/char/broadcom/bcm2835-gpiomem.c
  41 @@ -0,0 +1,258 @@
  42 +/**
  43 + * GPIO memory device driver
  44 + *
  45 + * Creates a chardev /dev/gpiomem which will provide user access to
  46 + * the BCM2835's GPIO registers when it is mmap()'d.
  47 + * No longer need root for user GPIO access, but without relaxing permissions
  48 + * on /dev/mem.
  49 + *
  50 + * Written by Luke Wren <luke@raspberrypi.org>
  51 + * Copyright (c) 2015, Raspberry Pi (Trading) Ltd.
  52 + *
  53 + * Redistribution and use in source and binary forms, with or without
  54 + * modification, are permitted provided that the following conditions
  55 + * are met:
  56 + * 1. Redistributions of source code must retain the above copyright
  57 + *    notice, this list of conditions, and the following disclaimer,
  58 + *    without modification.
  59 + * 2. Redistributions in binary form must reproduce the above copyright
  60 + *    notice, this list of conditions and the following disclaimer in the
  61 + *    documentation and/or other materials provided with the distribution.
  62 + * 3. The names of the above-listed copyright holders may not be used
  63 + *    to endorse or promote products derived from this software without
  64 + *    specific prior written permission.
  65 + *
  66 + * ALTERNATIVELY, this software may be distributed under the terms of the
  67 + * GNU General Public License ("GPL") version 2, as published by the Free
  68 + * Software Foundation.
  69 + *
  70 + * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS
  71 + * IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO,
  72 + * THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
  73 + * PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR
  74 + * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
  75 + * EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
  76 + * PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
  77 + * PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF
  78 + * LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
  79 + * NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
  80 + * SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  81 + */
  82 +
  83 +#include <linux/kernel.h>
  84 +#include <linux/module.h>
  85 +#include <linux/of.h>
  86 +#include <linux/platform_device.h>
  87 +#include <linux/mm.h>
  88 +#include <linux/slab.h>
  89 +#include <linux/cdev.h>
  90 +#include <linux/pagemap.h>
  91 +#include <linux/io.h>
  92 +
  93 +#define DEVICE_NAME "bcm2835-gpiomem"
  94 +#define DRIVER_NAME "gpiomem-bcm2835"
  95 +#define DEVICE_MINOR 0
  96 +
  97 +struct bcm2835_gpiomem_instance {
  98 +       unsigned long gpio_regs_phys;
  99 +       struct device *dev;
 100 +};
 101 +
 102 +static struct cdev bcm2835_gpiomem_cdev;
 103 +static dev_t bcm2835_gpiomem_devid;
 104 +static struct class *bcm2835_gpiomem_class;
 105 +static struct device *bcm2835_gpiomem_dev;
 106 +static struct bcm2835_gpiomem_instance *inst;
 107 +
 108 +
 109 +/****************************************************************************
 110 +*
 111 +*   GPIO mem chardev file ops
 112 +*
 113 +***************************************************************************/
 114 +
 115 +static int bcm2835_gpiomem_open(struct inode *inode, struct file *file)
 116 +{
 117 +       int dev = iminor(inode);
 118 +       int ret = 0;
 119 +
 120 +       if (dev != DEVICE_MINOR) {
 121 +               dev_err(inst->dev, "Unknown minor device: %d", dev);
 122 +               ret = -ENXIO;
 123 +       }
 124 +       return ret;
 125 +}
 126 +
 127 +static int bcm2835_gpiomem_release(struct inode *inode, struct file *file)
 128 +{
 129 +       int dev = iminor(inode);
 130 +       int ret = 0;
 131 +
 132 +       if (dev != DEVICE_MINOR) {
 133 +               dev_err(inst->dev, "Unknown minor device %d", dev);
 134 +               ret = -ENXIO;
 135 +       }
 136 +       return ret;
 137 +}
 138 +
 139 +static const struct vm_operations_struct bcm2835_gpiomem_vm_ops = {
 140 +#ifdef CONFIG_HAVE_IOREMAP_PROT
 141 +       .access = generic_access_phys
 142 +#endif
 143 +};
 144 +
 145 +static int bcm2835_gpiomem_mmap(struct file *file, struct vm_area_struct *vma)
 146 +{
 147 +       /* Ignore what the user says - they're getting the GPIO regs
 148 +          whether they like it or not! */
 149 +       unsigned long gpio_page = inst->gpio_regs_phys >> PAGE_SHIFT;
 150 +
 151 +       vma->vm_page_prot = phys_mem_access_prot(file, gpio_page,
 152 +                                                PAGE_SIZE,
 153 +                                                vma->vm_page_prot);
 154 +       vma->vm_ops = &bcm2835_gpiomem_vm_ops;
 155 +       if (remap_pfn_range(vma, vma->vm_start,
 156 +                       gpio_page,
 157 +                       PAGE_SIZE,
 158 +                       vma->vm_page_prot)) {
 159 +               return -EAGAIN;
 160 +       }
 161 +       return 0;
 162 +}
 163 +
 164 +static const struct file_operations
 165 +bcm2835_gpiomem_fops = {
 166 +       .owner = THIS_MODULE,
 167 +       .open = bcm2835_gpiomem_open,
 168 +       .release = bcm2835_gpiomem_release,
 169 +       .mmap = bcm2835_gpiomem_mmap,
 170 +};
 171 +
 172 +
 173 + /****************************************************************************
 174 +*
 175 +*   Probe and remove functions
 176 +*
 177 +***************************************************************************/
 178 +
 179 +
 180 +static int bcm2835_gpiomem_probe(struct platform_device *pdev)
 181 +{
 182 +       int err;
 183 +       void *ptr_err;
 184 +       struct device *dev = &pdev->dev;
 185 +       struct resource *ioresource;
 186 +
 187 +       /* Allocate buffers and instance data */
 188 +
 189 +       inst = kzalloc(sizeof(struct bcm2835_gpiomem_instance), GFP_KERNEL);
 190 +
 191 +       if (!inst) {
 192 +               err = -ENOMEM;
 193 +               goto failed_inst_alloc;
 194 +       }
 195 +
 196 +       inst->dev = dev;
 197 +
 198 +       ioresource = platform_get_resource(pdev, IORESOURCE_MEM, 0);
 199 +       if (ioresource) {
 200 +               inst->gpio_regs_phys = ioresource->start;
 201 +       } else {
 202 +               dev_err(inst->dev, "failed to get IO resource");
 203 +               err = -ENOENT;
 204 +               goto failed_get_resource;
 205 +       }
 206 +
 207 +       /* Create character device entries */
 208 +
 209 +       err = alloc_chrdev_region(&bcm2835_gpiomem_devid,
 210 +                                 DEVICE_MINOR, 1, DEVICE_NAME);
 211 +       if (err != 0) {
 212 +               dev_err(inst->dev, "unable to allocate device number");
 213 +               goto failed_alloc_chrdev;
 214 +       }
 215 +       cdev_init(&bcm2835_gpiomem_cdev, &bcm2835_gpiomem_fops);
 216 +       bcm2835_gpiomem_cdev.owner = THIS_MODULE;
 217 +       err = cdev_add(&bcm2835_gpiomem_cdev, bcm2835_gpiomem_devid, 1);
 218 +       if (err != 0) {
 219 +               dev_err(inst->dev, "unable to register device");
 220 +               goto failed_cdev_add;
 221 +       }
 222 +
 223 +       /* Create sysfs entries */
 224 +
 225 +       bcm2835_gpiomem_class = class_create(THIS_MODULE, DEVICE_NAME);
 226 +       ptr_err = bcm2835_gpiomem_class;
 227 +       if (IS_ERR(ptr_err))
 228 +               goto failed_class_create;
 229 +
 230 +       bcm2835_gpiomem_dev = device_create(bcm2835_gpiomem_class, NULL,
 231 +                                       bcm2835_gpiomem_devid, NULL,
 232 +                                       "gpiomem");
 233 +       ptr_err = bcm2835_gpiomem_dev;
 234 +       if (IS_ERR(ptr_err))
 235 +               goto failed_device_create;
 236 +
 237 +       dev_info(inst->dev, "Initialised: Registers at 0x%08lx",
 238 +               inst->gpio_regs_phys);
 239 +
 240 +       return 0;
 241 +
 242 +failed_device_create:
 243 +       class_destroy(bcm2835_gpiomem_class);
 244 +failed_class_create:
 245 +       cdev_del(&bcm2835_gpiomem_cdev);
 246 +       err = PTR_ERR(ptr_err);
 247 +failed_cdev_add:
 248 +       unregister_chrdev_region(bcm2835_gpiomem_devid, 1);
 249 +failed_alloc_chrdev:
 250 +failed_get_resource:
 251 +       kfree(inst);
 252 +failed_inst_alloc:
 253 +       dev_err(inst->dev, "could not load bcm2835_gpiomem");
 254 +       return err;
 255 +}
 256 +
 257 +static int bcm2835_gpiomem_remove(struct platform_device *pdev)
 258 +{
 259 +       struct device *dev = inst->dev;
 260 +
 261 +       kfree(inst);
 262 +       device_destroy(bcm2835_gpiomem_class, bcm2835_gpiomem_devid);
 263 +       class_destroy(bcm2835_gpiomem_class);
 264 +       cdev_del(&bcm2835_gpiomem_cdev);
 265 +       unregister_chrdev_region(bcm2835_gpiomem_devid, 1);
 266 +
 267 +       dev_info(dev, "GPIO mem driver removed - OK");
 268 +       return 0;
 269 +}
 270 +
 271 + /****************************************************************************
 272 +*
 273 +*   Register the driver with device tree
 274 +*
 275 +***************************************************************************/
 276 +
 277 +static const struct of_device_id bcm2835_gpiomem_of_match[] = {
 278 +       {.compatible = "brcm,bcm2835-gpiomem",},
 279 +       { /* sentinel */ },
 280 +};
 281 +
 282 +MODULE_DEVICE_TABLE(of, bcm2835_gpiomem_of_match);
 283 +
 284 +static struct platform_driver bcm2835_gpiomem_driver = {
 285 +       .probe = bcm2835_gpiomem_probe,
 286 +       .remove = bcm2835_gpiomem_remove,
 287 +       .driver = {
 288 +                  .name = DRIVER_NAME,
 289 +                  .owner = THIS_MODULE,
 290 +                  .of_match_table = bcm2835_gpiomem_of_match,
 291 +                  },
 292 +};
 293 +
 294 +module_platform_driver(bcm2835_gpiomem_driver);
 295 +
 296 +MODULE_ALIAS("platform:gpiomem-bcm2835");
 297 +MODULE_LICENSE("GPL");
 298 +MODULE_DESCRIPTION("gpiomem driver for accessing GPIO from userspace");
 299 +MODULE_AUTHOR("Luke Wren <luke@raspberrypi.org>");