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   1 From 1a2c16ef68cbba94eee5d916e77269bca572830d 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 048/703] 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           |   9 +
  15  drivers/char/broadcom/Makefile          |   3 +
  16  drivers/char/broadcom/bcm2835-gpiomem.c | 258 ++++++++++++++++++++++++
  17  3 files changed, 270 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 @@ -26,3 +26,12 @@ config BCM_VC_SM
  23         help
  24         Support for the VC shared memory on the Broadcom reference
  25         design. Uses the VCHIQ stack.
  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 +
  35 --- a/drivers/char/broadcom/Makefile
  36 +++ b/drivers/char/broadcom/Makefile
  37 @@ -1,2 +1,5 @@
  38  obj-$(CONFIG_BCM2708_VCMEM)    += vc_mem.o
  39  obj-$(CONFIG_BCM_VC_SM)         += vc_sm/
  40 +
  41 +obj-$(CONFIG_BCM2835_DEVGPIOMEM)+= bcm2835-gpiomem.o
  42 +
  43 --- /dev/null
  44 +++ b/drivers/char/broadcom/bcm2835-gpiomem.c
  45 @@ -0,0 +1,258 @@
  46 +/**
  47 + * GPIO memory device driver
  48 + *
  49 + * Creates a chardev /dev/gpiomem which will provide user access to
  50 + * the BCM2835's GPIO registers when it is mmap()'d.
  51 + * No longer need root for user GPIO access, but without relaxing permissions
  52 + * on /dev/mem.
  53 + *
  54 + * Written by Luke Wren <luke@raspberrypi.org>
  55 + * Copyright (c) 2015, Raspberry Pi (Trading) Ltd.
  56 + *
  57 + * Redistribution and use in source and binary forms, with or without
  58 + * modification, are permitted provided that the following conditions
  59 + * are met:
  60 + * 1. Redistributions of source code must retain the above copyright
  61 + *    notice, this list of conditions, and the following disclaimer,
  62 + *    without modification.
  63 + * 2. Redistributions in binary form must reproduce the above copyright
  64 + *    notice, this list of conditions and the following disclaimer in the
  65 + *    documentation and/or other materials provided with the distribution.
  66 + * 3. The names of the above-listed copyright holders may not be used
  67 + *    to endorse or promote products derived from this software without
  68 + *    specific prior written permission.
  69 + *
  70 + * ALTERNATIVELY, this software may be distributed under the terms of the
  71 + * GNU General Public License ("GPL") version 2, as published by the Free
  72 + * Software Foundation.
  73 + *
  74 + * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS
  75 + * IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO,
  76 + * THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
  77 + * PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR
  78 + * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
  79 + * EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
  80 + * PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
  81 + * PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF
  82 + * LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
  83 + * NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
  84 + * SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  85 + */
  86 +
  87 +#include <linux/kernel.h>
  88 +#include <linux/module.h>
  89 +#include <linux/of.h>
  90 +#include <linux/platform_device.h>
  91 +#include <linux/mm.h>
  92 +#include <linux/slab.h>
  93 +#include <linux/cdev.h>
  94 +#include <linux/pagemap.h>
  95 +#include <linux/io.h>
  96 +
  97 +#define DEVICE_NAME "bcm2835-gpiomem"
  98 +#define DRIVER_NAME "gpiomem-bcm2835"
  99 +#define DEVICE_MINOR 0
 100 +
 101 +struct bcm2835_gpiomem_instance {
 102 +       unsigned long gpio_regs_phys;
 103 +       struct device *dev;
 104 +};
 105 +
 106 +static struct cdev bcm2835_gpiomem_cdev;
 107 +static dev_t bcm2835_gpiomem_devid;
 108 +static struct class *bcm2835_gpiomem_class;
 109 +static struct device *bcm2835_gpiomem_dev;
 110 +static struct bcm2835_gpiomem_instance *inst;
 111 +
 112 +
 113 +/****************************************************************************
 114 +*
 115 +*   GPIO mem chardev file ops
 116 +*
 117 +***************************************************************************/
 118 +
 119 +static int bcm2835_gpiomem_open(struct inode *inode, struct file *file)
 120 +{
 121 +       int dev = iminor(inode);
 122 +       int ret = 0;
 123 +
 124 +       if (dev != DEVICE_MINOR) {
 125 +               dev_err(inst->dev, "Unknown minor device: %d", dev);
 126 +               ret = -ENXIO;
 127 +       }
 128 +       return ret;
 129 +}
 130 +
 131 +static int bcm2835_gpiomem_release(struct inode *inode, struct file *file)
 132 +{
 133 +       int dev = iminor(inode);
 134 +       int ret = 0;
 135 +
 136 +       if (dev != DEVICE_MINOR) {
 137 +               dev_err(inst->dev, "Unknown minor device %d", dev);
 138 +               ret = -ENXIO;
 139 +       }
 140 +       return ret;
 141 +}
 142 +
 143 +static const struct vm_operations_struct bcm2835_gpiomem_vm_ops = {
 144 +#ifdef CONFIG_HAVE_IOREMAP_PROT
 145 +       .access = generic_access_phys
 146 +#endif
 147 +};
 148 +
 149 +static int bcm2835_gpiomem_mmap(struct file *file, struct vm_area_struct *vma)
 150 +{
 151 +       /* Ignore what the user says - they're getting the GPIO regs
 152 +          whether they like it or not! */
 153 +       unsigned long gpio_page = inst->gpio_regs_phys >> PAGE_SHIFT;
 154 +
 155 +       vma->vm_page_prot = phys_mem_access_prot(file, gpio_page,
 156 +                                                PAGE_SIZE,
 157 +                                                vma->vm_page_prot);
 158 +       vma->vm_ops = &bcm2835_gpiomem_vm_ops;
 159 +       if (remap_pfn_range(vma, vma->vm_start,
 160 +                       gpio_page,
 161 +                       PAGE_SIZE,
 162 +                       vma->vm_page_prot)) {
 163 +               return -EAGAIN;
 164 +       }
 165 +       return 0;
 166 +}
 167 +
 168 +static const struct file_operations
 169 +bcm2835_gpiomem_fops = {
 170 +       .owner = THIS_MODULE,
 171 +       .open = bcm2835_gpiomem_open,
 172 +       .release = bcm2835_gpiomem_release,
 173 +       .mmap = bcm2835_gpiomem_mmap,
 174 +};
 175 +
 176 +
 177 + /****************************************************************************
 178 +*
 179 +*   Probe and remove functions
 180 +*
 181 +***************************************************************************/
 182 +
 183 +
 184 +static int bcm2835_gpiomem_probe(struct platform_device *pdev)
 185 +{
 186 +       int err;
 187 +       void *ptr_err;
 188 +       struct device *dev = &pdev->dev;
 189 +       struct resource *ioresource;
 190 +
 191 +       /* Allocate buffers and instance data */
 192 +
 193 +       inst = kzalloc(sizeof(struct bcm2835_gpiomem_instance), GFP_KERNEL);
 194 +
 195 +       if (!inst) {
 196 +               err = -ENOMEM;
 197 +               goto failed_inst_alloc;
 198 +       }
 199 +
 200 +       inst->dev = dev;
 201 +
 202 +       ioresource = platform_get_resource(pdev, IORESOURCE_MEM, 0);
 203 +       if (ioresource) {
 204 +               inst->gpio_regs_phys = ioresource->start;
 205 +       } else {
 206 +               dev_err(inst->dev, "failed to get IO resource");
 207 +               err = -ENOENT;
 208 +               goto failed_get_resource;
 209 +       }
 210 +
 211 +       /* Create character device entries */
 212 +
 213 +       err = alloc_chrdev_region(&bcm2835_gpiomem_devid,
 214 +                                 DEVICE_MINOR, 1, DEVICE_NAME);
 215 +       if (err != 0) {
 216 +               dev_err(inst->dev, "unable to allocate device number");
 217 +               goto failed_alloc_chrdev;
 218 +       }
 219 +       cdev_init(&bcm2835_gpiomem_cdev, &bcm2835_gpiomem_fops);
 220 +       bcm2835_gpiomem_cdev.owner = THIS_MODULE;
 221 +       err = cdev_add(&bcm2835_gpiomem_cdev, bcm2835_gpiomem_devid, 1);
 222 +       if (err != 0) {
 223 +               dev_err(inst->dev, "unable to register device");
 224 +               goto failed_cdev_add;
 225 +       }
 226 +
 227 +       /* Create sysfs entries */
 228 +
 229 +       bcm2835_gpiomem_class = class_create(THIS_MODULE, DEVICE_NAME);
 230 +       ptr_err = bcm2835_gpiomem_class;
 231 +       if (IS_ERR(ptr_err))
 232 +               goto failed_class_create;
 233 +
 234 +       bcm2835_gpiomem_dev = device_create(bcm2835_gpiomem_class, NULL,
 235 +                                       bcm2835_gpiomem_devid, NULL,
 236 +                                       "gpiomem");
 237 +       ptr_err = bcm2835_gpiomem_dev;
 238 +       if (IS_ERR(ptr_err))
 239 +               goto failed_device_create;
 240 +
 241 +       dev_info(inst->dev, "Initialised: Registers at 0x%08lx",
 242 +               inst->gpio_regs_phys);
 243 +
 244 +       return 0;
 245 +
 246 +failed_device_create:
 247 +       class_destroy(bcm2835_gpiomem_class);
 248 +failed_class_create:
 249 +       cdev_del(&bcm2835_gpiomem_cdev);
 250 +       err = PTR_ERR(ptr_err);
 251 +failed_cdev_add:
 252 +       unregister_chrdev_region(bcm2835_gpiomem_devid, 1);
 253 +failed_alloc_chrdev:
 254 +failed_get_resource:
 255 +       kfree(inst);
 256 +failed_inst_alloc:
 257 +       dev_err(inst->dev, "could not load bcm2835_gpiomem");
 258 +       return err;
 259 +}
 260 +
 261 +static int bcm2835_gpiomem_remove(struct platform_device *pdev)
 262 +{
 263 +       struct device *dev = inst->dev;
 264 +
 265 +       kfree(inst);
 266 +       device_destroy(bcm2835_gpiomem_class, bcm2835_gpiomem_devid);
 267 +       class_destroy(bcm2835_gpiomem_class);
 268 +       cdev_del(&bcm2835_gpiomem_cdev);
 269 +       unregister_chrdev_region(bcm2835_gpiomem_devid, 1);
 270 +
 271 +       dev_info(dev, "GPIO mem driver removed - OK");
 272 +       return 0;
 273 +}
 274 +
 275 + /****************************************************************************
 276 +*
 277 +*   Register the driver with device tree
 278 +*
 279 +***************************************************************************/
 280 +
 281 +static const struct of_device_id bcm2835_gpiomem_of_match[] = {
 282 +       {.compatible = "brcm,bcm2835-gpiomem",},
 283 +       { /* sentinel */ },
 284 +};
 285 +
 286 +MODULE_DEVICE_TABLE(of, bcm2835_gpiomem_of_match);
 287 +
 288 +static struct platform_driver bcm2835_gpiomem_driver = {
 289 +       .probe = bcm2835_gpiomem_probe,
 290 +       .remove = bcm2835_gpiomem_remove,
 291 +       .driver = {
 292 +                  .name = DRIVER_NAME,
 293 +                  .owner = THIS_MODULE,
 294 +                  .of_match_table = bcm2835_gpiomem_of_match,
 295 +                  },
 296 +};
 297 +
 298 +module_platform_driver(bcm2835_gpiomem_driver);
 299 +
 300 +MODULE_ALIAS("platform:gpiomem-bcm2835");
 301 +MODULE_LICENSE("GPL");
 302 +MODULE_DESCRIPTION("gpiomem driver for accessing GPIO from userspace");
 303 +MODULE_AUTHOR("Luke Wren <luke@raspberrypi.org>");