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openwrt-owl/target/linux/brcm2708/patches-4.4/0039-Add-dev-gpiomem-device...

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From e52d7ce66319f6687da3531b00cfec3001aec7a8 Mon Sep 17 00:00:00 2001
From: Luke Wren <luke@raspberrypi.org>
Date: Fri, 21 Aug 2015 23:14:48 +0100
Subject: [PATCH] Add /dev/gpiomem device for rootless user GPIO access
Signed-off-by: Luke Wren <luke@raspberrypi.org>
bcm2835-gpiomem: Fix for ARCH_BCM2835 builds
Build on ARCH_BCM2835, and fail to probe if no IO resource.
See: https://github.com/raspberrypi/linux/issues/1154
---
drivers/char/broadcom/Kconfig | 9 ++
drivers/char/broadcom/Makefile | 3 +
drivers/char/broadcom/bcm2835-gpiomem.c | 260 ++++++++++++++++++++++++++++++++
3 files changed, 272 insertions(+)
create mode 100644 drivers/char/broadcom/bcm2835-gpiomem.c
--- a/drivers/char/broadcom/Kconfig
+++ b/drivers/char/broadcom/Kconfig
@@ -32,3 +32,12 @@ config BCM_VC_SM
help
Support for the VC shared memory on the Broadcom reference
design. Uses the VCHIQ stack.
+
+config BCM2835_DEVGPIOMEM
+ tristate "/dev/gpiomem rootless GPIO access via mmap() on the BCM2835"
+ default m
+ help
+ Provides users with root-free access to the GPIO registers
+ on the 2835. Calling mmap(/dev/gpiomem) will map the GPIO
+ register page to the user's pointer.
+
--- a/drivers/char/broadcom/Makefile
+++ b/drivers/char/broadcom/Makefile
@@ -1,3 +1,6 @@
obj-$(CONFIG_BCM_VC_CMA) += vc_cma/
obj-$(CONFIG_BCM2708_VCMEM) += vc_mem.o
obj-$(CONFIG_BCM_VC_SM) += vc_sm/
+
+obj-$(CONFIG_BCM2835_DEVGPIOMEM)+= bcm2835-gpiomem.o
+
--- /dev/null
+++ b/drivers/char/broadcom/bcm2835-gpiomem.c
@@ -0,0 +1,260 @@
+/**
+ * GPIO memory device driver
+ *
+ * Creates a chardev /dev/gpiomem which will provide user access to
+ * the BCM2835's GPIO registers when it is mmap()'d.
+ * No longer need root for user GPIO access, but without relaxing permissions
+ * on /dev/mem.
+ *
+ * Written by Luke Wren <luke@raspberrypi.org>
+ * Copyright (c) 2015, Raspberry Pi (Trading) Ltd.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ * 1. Redistributions of source code must retain the above copyright
+ * notice, this list of conditions, and the following disclaimer,
+ * without modification.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ * notice, this list of conditions and the following disclaimer in the
+ * documentation and/or other materials provided with the distribution.
+ * 3. The names of the above-listed copyright holders may not be used
+ * to endorse or promote products derived from this software without
+ * specific prior written permission.
+ *
+ * ALTERNATIVELY, this software may be distributed under the terms of the
+ * GNU General Public License ("GPL") version 2, as published by the Free
+ * Software Foundation.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS
+ * IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO,
+ * THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
+ * PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR
+ * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
+ * EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
+ * PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
+ * PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF
+ * LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
+ * NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
+ * SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ */
+
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/of.h>
+#include <linux/platform_device.h>
+#include <linux/mm.h>
+#include <linux/slab.h>
+#include <linux/cdev.h>
+#include <linux/pagemap.h>
+#include <linux/io.h>
+
+#define DEVICE_NAME "bcm2835-gpiomem"
+#define DRIVER_NAME "gpiomem-bcm2835"
+#define DEVICE_MINOR 0
+
+struct bcm2835_gpiomem_instance {
+ unsigned long gpio_regs_phys;
+ struct device *dev;
+};
+
+static struct cdev bcm2835_gpiomem_cdev;
+static dev_t bcm2835_gpiomem_devid;
+static struct class *bcm2835_gpiomem_class;
+static struct device *bcm2835_gpiomem_dev;
+static struct bcm2835_gpiomem_instance *inst;
+
+
+/****************************************************************************
+*
+* GPIO mem chardev file ops
+*
+***************************************************************************/
+
+static int bcm2835_gpiomem_open(struct inode *inode, struct file *file)
+{
+ int dev = iminor(inode);
+ int ret = 0;
+
+ dev_info(inst->dev, "gpiomem device opened.");
+
+ if (dev != DEVICE_MINOR) {
+ dev_err(inst->dev, "Unknown minor device: %d", dev);
+ ret = -ENXIO;
+ }
+ return ret;
+}
+
+static int bcm2835_gpiomem_release(struct inode *inode, struct file *file)
+{
+ int dev = iminor(inode);
+ int ret = 0;
+
+ if (dev != DEVICE_MINOR) {
+ dev_err(inst->dev, "Unknown minor device %d", dev);
+ ret = -ENXIO;
+ }
+ return ret;
+}
+
+static const struct vm_operations_struct bcm2835_gpiomem_vm_ops = {
+#ifdef CONFIG_HAVE_IOREMAP_PROT
+ .access = generic_access_phys
+#endif
+};
+
+static int bcm2835_gpiomem_mmap(struct file *file, struct vm_area_struct *vma)
+{
+ /* Ignore what the user says - they're getting the GPIO regs
+ whether they like it or not! */
+ unsigned long gpio_page = inst->gpio_regs_phys >> PAGE_SHIFT;
+
+ vma->vm_page_prot = phys_mem_access_prot(file, gpio_page,
+ PAGE_SIZE,
+ vma->vm_page_prot);
+ vma->vm_ops = &bcm2835_gpiomem_vm_ops;
+ if (remap_pfn_range(vma, vma->vm_start,
+ gpio_page,
+ PAGE_SIZE,
+ vma->vm_page_prot)) {
+ return -EAGAIN;
+ }
+ return 0;
+}
+
+static const struct file_operations
+bcm2835_gpiomem_fops = {
+ .owner = THIS_MODULE,
+ .open = bcm2835_gpiomem_open,
+ .release = bcm2835_gpiomem_release,
+ .mmap = bcm2835_gpiomem_mmap,
+};
+
+
+ /****************************************************************************
+*
+* Probe and remove functions
+*
+***************************************************************************/
+
+
+static int bcm2835_gpiomem_probe(struct platform_device *pdev)
+{
+ int err;
+ void *ptr_err;
+ struct device *dev = &pdev->dev;
+ struct resource *ioresource;
+
+ /* Allocate buffers and instance data */
+
+ inst = kzalloc(sizeof(struct bcm2835_gpiomem_instance), GFP_KERNEL);
+
+ if (!inst) {
+ err = -ENOMEM;
+ goto failed_inst_alloc;
+ }
+
+ inst->dev = dev;
+
+ ioresource = platform_get_resource(pdev, IORESOURCE_MEM, 0);
+ if (ioresource) {
+ inst->gpio_regs_phys = ioresource->start;
+ } else {
+ dev_err(inst->dev, "failed to get IO resource");
+ err = -ENOENT;
+ goto failed_get_resource;
+ }
+
+ /* Create character device entries */
+
+ err = alloc_chrdev_region(&bcm2835_gpiomem_devid,
+ DEVICE_MINOR, 1, DEVICE_NAME);
+ if (err != 0) {
+ dev_err(inst->dev, "unable to allocate device number");
+ goto failed_alloc_chrdev;
+ }
+ cdev_init(&bcm2835_gpiomem_cdev, &bcm2835_gpiomem_fops);
+ bcm2835_gpiomem_cdev.owner = THIS_MODULE;
+ err = cdev_add(&bcm2835_gpiomem_cdev, bcm2835_gpiomem_devid, 1);
+ if (err != 0) {
+ dev_err(inst->dev, "unable to register device");
+ goto failed_cdev_add;
+ }
+
+ /* Create sysfs entries */
+
+ bcm2835_gpiomem_class = class_create(THIS_MODULE, DEVICE_NAME);
+ ptr_err = bcm2835_gpiomem_class;
+ if (IS_ERR(ptr_err))
+ goto failed_class_create;
+
+ bcm2835_gpiomem_dev = device_create(bcm2835_gpiomem_class, NULL,
+ bcm2835_gpiomem_devid, NULL,
+ "gpiomem");
+ ptr_err = bcm2835_gpiomem_dev;
+ if (IS_ERR(ptr_err))
+ goto failed_device_create;
+
+ dev_info(inst->dev, "Initialised: Registers at 0x%08lx",
+ inst->gpio_regs_phys);
+
+ return 0;
+
+failed_device_create:
+ class_destroy(bcm2835_gpiomem_class);
+failed_class_create:
+ cdev_del(&bcm2835_gpiomem_cdev);
+ err = PTR_ERR(ptr_err);
+failed_cdev_add:
+ unregister_chrdev_region(bcm2835_gpiomem_devid, 1);
+failed_alloc_chrdev:
+failed_get_resource:
+ kfree(inst);
+failed_inst_alloc:
+ dev_err(inst->dev, "could not load bcm2835_gpiomem");
+ return err;
+}
+
+static int bcm2835_gpiomem_remove(struct platform_device *pdev)
+{
+ struct device *dev = inst->dev;
+
+ kfree(inst);
+ device_destroy(bcm2835_gpiomem_class, bcm2835_gpiomem_devid);
+ class_destroy(bcm2835_gpiomem_class);
+ cdev_del(&bcm2835_gpiomem_cdev);
+ unregister_chrdev_region(bcm2835_gpiomem_devid, 1);
+
+ dev_info(dev, "GPIO mem driver removed - OK");
+ return 0;
+}
+
+ /****************************************************************************
+*
+* Register the driver with device tree
+*
+***************************************************************************/
+
+static const struct of_device_id bcm2835_gpiomem_of_match[] = {
+ {.compatible = "brcm,bcm2835-gpiomem",},
+ { /* sentinel */ },
+};
+
+MODULE_DEVICE_TABLE(of, bcm2835_gpiomem_of_match);
+
+static struct platform_driver bcm2835_gpiomem_driver = {
+ .probe = bcm2835_gpiomem_probe,
+ .remove = bcm2835_gpiomem_remove,
+ .driver = {
+ .name = DRIVER_NAME,
+ .owner = THIS_MODULE,
+ .of_match_table = bcm2835_gpiomem_of_match,
+ },
+};
+
+module_platform_driver(bcm2835_gpiomem_driver);
+
+MODULE_ALIAS("platform:gpiomem-bcm2835");
+MODULE_LICENSE("GPL");
+MODULE_DESCRIPTION("gpiomem driver for accessing GPIO from userspace");
+MODULE_AUTHOR("Luke Wren <luke@raspberrypi.org>");
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