300 lines
9.0 KiB
Diff
300 lines
9.0 KiB
Diff
From 09897ac552d99d483131bcf107866ac2dc51694f Mon Sep 17 00:00:00 2001
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From: Luke Wren <luke@raspberrypi.org>
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Date: Fri, 21 Aug 2015 23:14:48 +0100
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Subject: [PATCH] Add /dev/gpiomem device for rootless user GPIO access
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Signed-off-by: Luke Wren <luke@raspberrypi.org>
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bcm2835-gpiomem: Fix for ARCH_BCM2835 builds
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Build on ARCH_BCM2835, and fail to probe if no IO resource.
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See: https://github.com/raspberrypi/linux/issues/1154
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---
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drivers/char/broadcom/Kconfig | 8 +
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drivers/char/broadcom/Makefile | 1 +
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drivers/char/broadcom/bcm2835-gpiomem.c | 258 ++++++++++++++++++++++++
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3 files changed, 267 insertions(+)
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create mode 100644 drivers/char/broadcom/bcm2835-gpiomem.c
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--- a/drivers/char/broadcom/Kconfig
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+++ b/drivers/char/broadcom/Kconfig
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@@ -16,3 +16,11 @@ config BCM2708_VCMEM
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Helper for videocore memory access and total size allocation.
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endif
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+
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+config BCM2835_DEVGPIOMEM
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+ tristate "/dev/gpiomem rootless GPIO access via mmap() on the BCM2835"
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+ default m
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+ help
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+ Provides users with root-free access to the GPIO registers
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+ on the 2835. Calling mmap(/dev/gpiomem) will map the GPIO
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+ register page to the user's pointer.
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--- a/drivers/char/broadcom/Makefile
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+++ b/drivers/char/broadcom/Makefile
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@@ -1 +1,2 @@
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obj-$(CONFIG_BCM2708_VCMEM) += vc_mem.o
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+obj-$(CONFIG_BCM2835_DEVGPIOMEM)+= bcm2835-gpiomem.o
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--- /dev/null
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+++ b/drivers/char/broadcom/bcm2835-gpiomem.c
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@@ -0,0 +1,258 @@
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+/**
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+ * GPIO memory device driver
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+ *
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+ * Creates a chardev /dev/gpiomem which will provide user access to
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+ * the BCM2835's GPIO registers when it is mmap()'d.
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+ * No longer need root for user GPIO access, but without relaxing permissions
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+ * on /dev/mem.
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+ *
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+ * Written by Luke Wren <luke@raspberrypi.org>
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+ * Copyright (c) 2015, Raspberry Pi (Trading) Ltd.
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+ *
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+ * Redistribution and use in source and binary forms, with or without
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+ * modification, are permitted provided that the following conditions
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+ * are met:
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+ * 1. Redistributions of source code must retain the above copyright
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+ * notice, this list of conditions, and the following disclaimer,
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+ * without modification.
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+ * 2. Redistributions in binary form must reproduce the above copyright
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+ * notice, this list of conditions and the following disclaimer in the
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+ * documentation and/or other materials provided with the distribution.
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+ * 3. The names of the above-listed copyright holders may not be used
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+ * to endorse or promote products derived from this software without
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+ * specific prior written permission.
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+ *
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+ * ALTERNATIVELY, this software may be distributed under the terms of the
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+ * GNU General Public License ("GPL") version 2, as published by the Free
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+ * Software Foundation.
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+ *
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+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS
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+ * IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO,
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+ * THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
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+ * PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR
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+ * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
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+ * EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
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+ * PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
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+ * PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF
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+ * LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
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+ * NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
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+ * SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
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+ */
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+
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+#include <linux/kernel.h>
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+#include <linux/module.h>
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+#include <linux/of.h>
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+#include <linux/platform_device.h>
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+#include <linux/mm.h>
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+#include <linux/slab.h>
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+#include <linux/cdev.h>
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+#include <linux/pagemap.h>
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+#include <linux/io.h>
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+
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+#define DEVICE_NAME "bcm2835-gpiomem"
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+#define DRIVER_NAME "gpiomem-bcm2835"
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+#define DEVICE_MINOR 0
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+
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+struct bcm2835_gpiomem_instance {
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+ unsigned long gpio_regs_phys;
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+ struct device *dev;
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+};
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+
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+static struct cdev bcm2835_gpiomem_cdev;
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+static dev_t bcm2835_gpiomem_devid;
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+static struct class *bcm2835_gpiomem_class;
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+static struct device *bcm2835_gpiomem_dev;
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+static struct bcm2835_gpiomem_instance *inst;
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+
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+
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+/****************************************************************************
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+*
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+* GPIO mem chardev file ops
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+*
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+***************************************************************************/
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+
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+static int bcm2835_gpiomem_open(struct inode *inode, struct file *file)
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+{
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+ int dev = iminor(inode);
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+ int ret = 0;
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+
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+ if (dev != DEVICE_MINOR) {
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+ dev_err(inst->dev, "Unknown minor device: %d", dev);
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+ ret = -ENXIO;
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+ }
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+ return ret;
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+}
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+
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+static int bcm2835_gpiomem_release(struct inode *inode, struct file *file)
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+{
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+ int dev = iminor(inode);
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+ int ret = 0;
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+
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+ if (dev != DEVICE_MINOR) {
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+ dev_err(inst->dev, "Unknown minor device %d", dev);
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+ ret = -ENXIO;
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+ }
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+ return ret;
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+}
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+
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+static const struct vm_operations_struct bcm2835_gpiomem_vm_ops = {
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+#ifdef CONFIG_HAVE_IOREMAP_PROT
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+ .access = generic_access_phys
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+#endif
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+};
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+
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+static int bcm2835_gpiomem_mmap(struct file *file, struct vm_area_struct *vma)
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+{
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+ /* Ignore what the user says - they're getting the GPIO regs
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+ whether they like it or not! */
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+ unsigned long gpio_page = inst->gpio_regs_phys >> PAGE_SHIFT;
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+
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+ vma->vm_page_prot = phys_mem_access_prot(file, gpio_page,
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+ PAGE_SIZE,
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+ vma->vm_page_prot);
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+ vma->vm_ops = &bcm2835_gpiomem_vm_ops;
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+ if (remap_pfn_range(vma, vma->vm_start,
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+ gpio_page,
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+ PAGE_SIZE,
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+ vma->vm_page_prot)) {
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+ return -EAGAIN;
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+ }
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+ return 0;
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+}
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+
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+static const struct file_operations
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+bcm2835_gpiomem_fops = {
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+ .owner = THIS_MODULE,
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+ .open = bcm2835_gpiomem_open,
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+ .release = bcm2835_gpiomem_release,
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+ .mmap = bcm2835_gpiomem_mmap,
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+};
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+
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+
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+ /****************************************************************************
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+*
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+* Probe and remove functions
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+*
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+***************************************************************************/
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+
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+
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+static int bcm2835_gpiomem_probe(struct platform_device *pdev)
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+{
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+ int err;
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+ void *ptr_err;
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+ struct device *dev = &pdev->dev;
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+ struct resource *ioresource;
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+
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+ /* Allocate buffers and instance data */
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+
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+ inst = kzalloc(sizeof(struct bcm2835_gpiomem_instance), GFP_KERNEL);
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+
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+ if (!inst) {
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+ err = -ENOMEM;
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+ goto failed_inst_alloc;
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+ }
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+
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+ inst->dev = dev;
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+
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+ ioresource = platform_get_resource(pdev, IORESOURCE_MEM, 0);
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+ if (ioresource) {
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+ inst->gpio_regs_phys = ioresource->start;
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+ } else {
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+ dev_err(inst->dev, "failed to get IO resource");
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+ err = -ENOENT;
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+ goto failed_get_resource;
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+ }
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+
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+ /* Create character device entries */
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+
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+ err = alloc_chrdev_region(&bcm2835_gpiomem_devid,
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+ DEVICE_MINOR, 1, DEVICE_NAME);
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+ if (err != 0) {
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+ dev_err(inst->dev, "unable to allocate device number");
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+ goto failed_alloc_chrdev;
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+ }
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+ cdev_init(&bcm2835_gpiomem_cdev, &bcm2835_gpiomem_fops);
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+ bcm2835_gpiomem_cdev.owner = THIS_MODULE;
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+ err = cdev_add(&bcm2835_gpiomem_cdev, bcm2835_gpiomem_devid, 1);
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+ if (err != 0) {
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+ dev_err(inst->dev, "unable to register device");
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+ goto failed_cdev_add;
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+ }
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+
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+ /* Create sysfs entries */
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+
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+ bcm2835_gpiomem_class = class_create(THIS_MODULE, DEVICE_NAME);
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+ ptr_err = bcm2835_gpiomem_class;
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+ if (IS_ERR(ptr_err))
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+ goto failed_class_create;
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+
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+ bcm2835_gpiomem_dev = device_create(bcm2835_gpiomem_class, NULL,
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+ bcm2835_gpiomem_devid, NULL,
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+ "gpiomem");
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+ ptr_err = bcm2835_gpiomem_dev;
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+ if (IS_ERR(ptr_err))
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+ goto failed_device_create;
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+
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+ dev_info(inst->dev, "Initialised: Registers at 0x%08lx",
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+ inst->gpio_regs_phys);
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+
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+ return 0;
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+
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+failed_device_create:
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+ class_destroy(bcm2835_gpiomem_class);
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+failed_class_create:
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+ cdev_del(&bcm2835_gpiomem_cdev);
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+ err = PTR_ERR(ptr_err);
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+failed_cdev_add:
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+ unregister_chrdev_region(bcm2835_gpiomem_devid, 1);
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+failed_alloc_chrdev:
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+failed_get_resource:
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+ kfree(inst);
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+failed_inst_alloc:
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+ dev_err(inst->dev, "could not load bcm2835_gpiomem");
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+ return err;
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+}
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+
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+static int bcm2835_gpiomem_remove(struct platform_device *pdev)
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+{
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+ struct device *dev = inst->dev;
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+
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+ kfree(inst);
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+ device_destroy(bcm2835_gpiomem_class, bcm2835_gpiomem_devid);
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+ class_destroy(bcm2835_gpiomem_class);
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+ cdev_del(&bcm2835_gpiomem_cdev);
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+ unregister_chrdev_region(bcm2835_gpiomem_devid, 1);
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+
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+ dev_info(dev, "GPIO mem driver removed - OK");
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+ return 0;
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+}
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+
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+ /****************************************************************************
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+*
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+* Register the driver with device tree
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+*
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+***************************************************************************/
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+
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+static const struct of_device_id bcm2835_gpiomem_of_match[] = {
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+ {.compatible = "brcm,bcm2835-gpiomem",},
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+ { /* sentinel */ },
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+};
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+
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+MODULE_DEVICE_TABLE(of, bcm2835_gpiomem_of_match);
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+
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+static struct platform_driver bcm2835_gpiomem_driver = {
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+ .probe = bcm2835_gpiomem_probe,
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+ .remove = bcm2835_gpiomem_remove,
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+ .driver = {
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+ .name = DRIVER_NAME,
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+ .owner = THIS_MODULE,
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+ .of_match_table = bcm2835_gpiomem_of_match,
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+ },
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+};
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+
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+module_platform_driver(bcm2835_gpiomem_driver);
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+
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+MODULE_ALIAS("platform:gpiomem-bcm2835");
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+MODULE_LICENSE("GPL");
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+MODULE_DESCRIPTION("gpiomem driver for accessing GPIO from userspace");
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+MODULE_AUTHOR("Luke Wren <luke@raspberrypi.org>");
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