target/linux/brcm2708/patches-4.4/0039-Add-dev-gpiomem-device-for-rootless-user-GPIO-access.patch

   1 From e52d7ce66319f6687da3531b00cfec3001aec7a8 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           |   9 ++
  15  drivers/char/broadcom/Makefile          |   3 +
  16  drivers/char/broadcom/bcm2835-gpiomem.c | 260 ++++++++++++++++++++++++++++++++
  17  3 files changed, 272 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 @@ -32,3 +32,12 @@ 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 @@ -1,3 +1,6 @@
  38  obj-$(CONFIG_BCM_VC_CMA)       += vc_cma/
  39  obj-$(CONFIG_BCM2708_VCMEM)    += vc_mem.o
  40  obj-$(CONFIG_BCM_VC_SM)         += vc_sm/
  41 +
  42 +obj-$(CONFIG_BCM2835_DEVGPIOMEM)+= bcm2835-gpiomem.o
  43 +
  44 --- /dev/null
  45 +++ b/drivers/char/broadcom/bcm2835-gpiomem.c
  46 @@ -0,0 +1,260 @@
  47 +/**
  48 + * GPIO memory device driver
  49 + *
  50 + * Creates a chardev /dev/gpiomem which will provide user access to
  51 + * the BCM2835's GPIO registers when it is mmap()'d.
  52 + * No longer need root for user GPIO access, but without relaxing permissions
  53 + * on /dev/mem.
  54 + *
  55 + * Written by Luke Wren <luke@raspberrypi.org>
  56 + * Copyright (c) 2015, Raspberry Pi (Trading) Ltd.
  57 + *
  58 + * Redistribution and use in source and binary forms, with or without
  59 + * modification, are permitted provided that the following conditions
  60 + * are met:
  61 + * 1. Redistributions of source code must retain the above copyright
  62 + *    notice, this list of conditions, and the following disclaimer,
  63 + *    without modification.
  64 + * 2. Redistributions in binary form must reproduce the above copyright
  65 + *    notice, this list of conditions and the following disclaimer in the
  66 + *    documentation and/or other materials provided with the distribution.
  67 + * 3. The names of the above-listed copyright holders may not be used
  68 + *    to endorse or promote products derived from this software without
  69 + *    specific prior written permission.
  70 + *
  71 + * ALTERNATIVELY, this software may be distributed under the terms of the
  72 + * GNU General Public License ("GPL") version 2, as published by the Free
  73 + * Software Foundation.
  74 + *
  75 + * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS
  76 + * IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO,
  77 + * THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
  78 + * PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR
  79 + * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
  80 + * EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
  81 + * PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
  82 + * PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF
  83 + * LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
  84 + * NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
  85 + * SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  86 + */
  87 +
  88 +#include <linux/kernel.h>
  89 +#include <linux/module.h>
  90 +#include <linux/of.h>
  91 +#include <linux/platform_device.h>
  92 +#include <linux/mm.h>
  93 +#include <linux/slab.h>
  94 +#include <linux/cdev.h>
  95 +#include <linux/pagemap.h>
  96 +#include <linux/io.h>
  97 +
  98 +#define DEVICE_NAME "bcm2835-gpiomem"
  99 +#define DRIVER_NAME "gpiomem-bcm2835"
 100 +#define DEVICE_MINOR 0
 101 +
 102 +struct bcm2835_gpiomem_instance {
 103 +       unsigned long gpio_regs_phys;
 104 +       struct device *dev;
 105 +};
 106 +
 107 +static struct cdev bcm2835_gpiomem_cdev;
 108 +static dev_t bcm2835_gpiomem_devid;
 109 +static struct class *bcm2835_gpiomem_class;
 110 +static struct device *bcm2835_gpiomem_dev;
 111 +static struct bcm2835_gpiomem_instance *inst;
 112 +
 113 +
 114 +/****************************************************************************
 115 +*
 116 +*   GPIO mem chardev file ops
 117 +*
 118 +***************************************************************************/
 119 +
 120 +static int bcm2835_gpiomem_open(struct inode *inode, struct file *file)
 121 +{
 122 +       int dev = iminor(inode);
 123 +       int ret = 0;
 124 +
 125 +       dev_info(inst->dev, "gpiomem device opened.");
 126 +
 127 +       if (dev != DEVICE_MINOR) {
 128 +               dev_err(inst->dev, "Unknown minor device: %d", dev);
 129 +               ret = -ENXIO;
 130 +       }
 131 +       return ret;
 132 +}
 133 +
 134 +static int bcm2835_gpiomem_release(struct inode *inode, struct file *file)
 135 +{
 136 +       int dev = iminor(inode);
 137 +       int ret = 0;
 138 +
 139 +       if (dev != DEVICE_MINOR) {
 140 +               dev_err(inst->dev, "Unknown minor device %d", dev);
 141 +               ret = -ENXIO;
 142 +       }
 143 +       return ret;
 144 +}
 145 +
 146 +static const struct vm_operations_struct bcm2835_gpiomem_vm_ops = {
 147 +#ifdef CONFIG_HAVE_IOREMAP_PROT
 148 +       .access = generic_access_phys
 149 +#endif
 150 +};
 151 +
 152 +static int bcm2835_gpiomem_mmap(struct file *file, struct vm_area_struct *vma)
 153 +{
 154 +       /* Ignore what the user says - they're getting the GPIO regs
 155 +          whether they like it or not! */
 156 +       unsigned long gpio_page = inst->gpio_regs_phys >> PAGE_SHIFT;
 157 +
 158 +       vma->vm_page_prot = phys_mem_access_prot(file, gpio_page,
 159 +                                                PAGE_SIZE,
 160 +                                                vma->vm_page_prot);
 161 +       vma->vm_ops = &bcm2835_gpiomem_vm_ops;
 162 +       if (remap_pfn_range(vma, vma->vm_start,
 163 +                       gpio_page,
 164 +                       PAGE_SIZE,
 165 +                       vma->vm_page_prot)) {
 166 +               return -EAGAIN;
 167 +       }
 168 +       return 0;
 169 +}
 170 +
 171 +static const struct file_operations
 172 +bcm2835_gpiomem_fops = {
 173 +       .owner = THIS_MODULE,
 174 +       .open = bcm2835_gpiomem_open,
 175 +       .release = bcm2835_gpiomem_release,
 176 +       .mmap = bcm2835_gpiomem_mmap,
 177 +};
 178 +
 179 +
 180 + /****************************************************************************
 181 +*
 182 +*   Probe and remove functions
 183 +*
 184 +***************************************************************************/
 185 +
 186 +
 187 +static int bcm2835_gpiomem_probe(struct platform_device *pdev)
 188 +{
 189 +       int err;
 190 +       void *ptr_err;
 191 +       struct device *dev = &pdev->dev;
 192 +       struct resource *ioresource;
 193 +
 194 +       /* Allocate buffers and instance data */
 195 +
 196 +       inst = kzalloc(sizeof(struct bcm2835_gpiomem_instance), GFP_KERNEL);
 197 +
 198 +       if (!inst) {
 199 +               err = -ENOMEM;
 200 +               goto failed_inst_alloc;
 201 +       }
 202 +
 203 +       inst->dev = dev;
 204 +
 205 +       ioresource = platform_get_resource(pdev, IORESOURCE_MEM, 0);
 206 +       if (ioresource) {
 207 +               inst->gpio_regs_phys = ioresource->start;
 208 +       } else {
 209 +               dev_err(inst->dev, "failed to get IO resource");
 210 +               err = -ENOENT;
 211 +               goto failed_get_resource;
 212 +       }
 213 +
 214 +       /* Create character device entries */
 215 +
 216 +       err = alloc_chrdev_region(&bcm2835_gpiomem_devid,
 217 +                                 DEVICE_MINOR, 1, DEVICE_NAME);
 218 +       if (err != 0) {
 219 +               dev_err(inst->dev, "unable to allocate device number");
 220 +               goto failed_alloc_chrdev;
 221 +       }
 222 +       cdev_init(&bcm2835_gpiomem_cdev, &bcm2835_gpiomem_fops);
 223 +       bcm2835_gpiomem_cdev.owner = THIS_MODULE;
 224 +       err = cdev_add(&bcm2835_gpiomem_cdev, bcm2835_gpiomem_devid, 1);
 225 +       if (err != 0) {
 226 +               dev_err(inst->dev, "unable to register device");
 227 +               goto failed_cdev_add;
 228 +       }
 229 +
 230 +       /* Create sysfs entries */
 231 +
 232 +       bcm2835_gpiomem_class = class_create(THIS_MODULE, DEVICE_NAME);
 233 +       ptr_err = bcm2835_gpiomem_class;
 234 +       if (IS_ERR(ptr_err))
 235 +               goto failed_class_create;
 236 +
 237 +       bcm2835_gpiomem_dev = device_create(bcm2835_gpiomem_class, NULL,
 238 +                                       bcm2835_gpiomem_devid, NULL,
 239 +                                       "gpiomem");
 240 +       ptr_err = bcm2835_gpiomem_dev;
 241 +       if (IS_ERR(ptr_err))
 242 +               goto failed_device_create;
 243 +
 244 +       dev_info(inst->dev, "Initialised: Registers at 0x%08lx",
 245 +               inst->gpio_regs_phys);
 246 +
 247 +       return 0;
 248 +
 249 +failed_device_create:
 250 +       class_destroy(bcm2835_gpiomem_class);
 251 +failed_class_create:
 252 +       cdev_del(&bcm2835_gpiomem_cdev);
 253 +       err = PTR_ERR(ptr_err);
 254 +failed_cdev_add:
 255 +       unregister_chrdev_region(bcm2835_gpiomem_devid, 1);
 256 +failed_alloc_chrdev:
 257 +failed_get_resource:
 258 +       kfree(inst);
 259 +failed_inst_alloc:
 260 +       dev_err(inst->dev, "could not load bcm2835_gpiomem");
 261 +       return err;
 262 +}
 263 +
 264 +static int bcm2835_gpiomem_remove(struct platform_device *pdev)
 265 +{
 266 +       struct device *dev = inst->dev;
 267 +
 268 +       kfree(inst);
 269 +       device_destroy(bcm2835_gpiomem_class, bcm2835_gpiomem_devid);
 270 +       class_destroy(bcm2835_gpiomem_class);
 271 +       cdev_del(&bcm2835_gpiomem_cdev);
 272 +       unregister_chrdev_region(bcm2835_gpiomem_devid, 1);
 273 +
 274 +       dev_info(dev, "GPIO mem driver removed - OK");
 275 +       return 0;
 276 +}
 277 +
 278 + /****************************************************************************
 279 +*
 280 +*   Register the driver with device tree
 281 +*
 282 +***************************************************************************/
 283 +
 284 +static const struct of_device_id bcm2835_gpiomem_of_match[] = {
 285 +       {.compatible = "brcm,bcm2835-gpiomem",},
 286 +       { /* sentinel */ },
 287 +};
 288 +
 289 +MODULE_DEVICE_TABLE(of, bcm2835_gpiomem_of_match);
 290 +
 291 +static struct platform_driver bcm2835_gpiomem_driver = {
 292 +       .probe = bcm2835_gpiomem_probe,
 293 +       .remove = bcm2835_gpiomem_remove,
 294 +       .driver = {
 295 +                  .name = DRIVER_NAME,
 296 +                  .owner = THIS_MODULE,
 297 +                  .of_match_table = bcm2835_gpiomem_of_match,
 298 +                  },
 299 +};
 300 +
 301 +module_platform_driver(bcm2835_gpiomem_driver);
 302 +
 303 +MODULE_ALIAS("platform:gpiomem-bcm2835");
 304 +MODULE_LICENSE("GPL");
 305 +MODULE_DESCRIPTION("gpiomem driver for accessing GPIO from userspace");
 306 +MODULE_AUTHOR("Luke Wren <luke@raspberrypi.org>");