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