mirror of
https://github.com/Ysurac/openmptcprouter.git
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328 lines
8.8 KiB
Diff
328 lines
8.8 KiB
Diff
From 7279a26a2f794997658ebf79acb79981d0b33d5a Mon Sep 17 00:00:00 2001
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From: Jonathan Bell <jonathan@raspberrypi.com>
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Date: Tue, 25 Apr 2023 15:52:13 +0100
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Subject: [PATCH] drivers: char: add generic gpiomem driver
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Based on bcm2835-gpiomem.
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We allow export of the "GPIO registers" to userspace via a chardev as
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this allows for finer access control (e.g. users must be group gpio, root
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not required).
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This driver allows access to either rp1-gpiomem or gpiomem, depending on
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which nodes are populated in devicetree.
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RP1 has a different look-and-feel to BCM283x SoCs as it has split ranges
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for IO controls and the parallel registered OE/IN/OUT access. To handle
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this, the driver concatenates the ranges for an IO bank and the
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corresponding RIO instance into a contiguous buffer.
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Signed-off-by: Jonathan Bell <jonathan@raspberrypi.com>
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---
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drivers/char/Kconfig | 8 +
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drivers/char/Makefile | 1 +
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drivers/char/raspberrypi-gpiomem.c | 276 +++++++++++++++++++++++++++++
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3 files changed, 285 insertions(+)
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create mode 100644 drivers/char/raspberrypi-gpiomem.c
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--- a/drivers/char/Kconfig
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+++ b/drivers/char/Kconfig
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@@ -461,4 +461,12 @@ config RANDOM_TRUST_BOOTLOADER
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believe its RNG facilities may be faulty. This may also be configured
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at boot time with "random.trust_bootloader=on/off".
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+config RASPBERRYPI_GPIOMEM
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+ tristate "Rootless GPIO access via mmap() on Raspberry Pi boards"
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+ default n
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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 board. Calling mmap(/dev/gpiomem) will map the GPIO
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+ register page to the user's pointer.
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+
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endmenu
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--- a/drivers/char/Makefile
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+++ b/drivers/char/Makefile
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@@ -46,3 +46,4 @@ obj-$(CONFIG_XILLYBUS_CLASS) += xillybus
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obj-$(CONFIG_POWERNV_OP_PANEL) += powernv-op-panel.o
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obj-$(CONFIG_ADI) += adi.o
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obj-$(CONFIG_BRCM_CHAR_DRIVERS) += broadcom/
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+obj-$(CONFIG_RASPBERRYPI_GPIOMEM) += raspberrypi-gpiomem.o
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--- /dev/null
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+++ b/drivers/char/raspberrypi-gpiomem.c
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@@ -0,0 +1,276 @@
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+// SPDX-License-Identifier: GPL-2.0 OR BSD-3-Clause
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+/**
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+ * raspberrypi-gpiomem.c
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+ *
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+ * Provides MMIO access to discontiguous section of Device memory as a linear
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+ * user mapping. Successor to bcm2835-gpiomem.c.
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+ *
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+ * Copyright (c) 2023, Raspberry Pi Ltd.
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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/of_device.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 DRIVER_NAME "rpi-gpiomem"
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+#define DEVICE_MINOR 0
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+
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+/*
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+ * Sensible max for a hypothetical "gpio" controller that splits pads,
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+ * IO controls, GPIO in/out/enable, and function selection into different
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+ * ranges. Most use only one or two.
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+ */
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+#define MAX_RANGES 4
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+
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+struct io_windows {
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+ unsigned long phys_base;
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+ unsigned long len;
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+};
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+
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+struct rpi_gpiomem_priv {
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+ dev_t devid;
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+ struct class *class;
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+ struct cdev rpi_gpiomem_cdev;
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+ struct device *dev;
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+ const char *name;
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+ unsigned int nr_wins;
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+ struct io_windows iowins[4];
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+};
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+
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+static int rpi_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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+ struct rpi_gpiomem_priv *priv;
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+
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+ if (dev != DEVICE_MINOR)
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+ ret = -ENXIO;
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+
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+ priv = container_of(inode->i_cdev, struct rpi_gpiomem_priv,
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+ rpi_gpiomem_cdev);
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+ if (!priv)
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+ return -EINVAL;
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+ file->private_data = priv;
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+ return ret;
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+}
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+
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+static int rpi_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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+ 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 rpi_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 rpi_gpiomem_mmap(struct file *file, struct vm_area_struct *vma)
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+{
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+ int i;
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+ struct rpi_gpiomem_priv *priv;
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+ unsigned long base;
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+ unsigned long len = 0;
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+ unsigned long offset;
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+
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+ priv = file->private_data;
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+ /*
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+ * Userspace must provide a virtual address space at least
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+ * the size of the concatenated ranges.
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+ */
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+ for (i = 0; i < priv->nr_wins; i++)
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+ len += priv->iowins[i].len;
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+ if (len > vma->vm_end - vma->vm_start + 1)
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+ return -EINVAL;
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+
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+ vma->vm_ops = &rpi_gpiomem_vm_ops;
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+ offset = vma->vm_start;
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+ for (i = 0; i < priv->nr_wins; i++) {
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+ base = priv->iowins[i].phys_base >> PAGE_SHIFT;
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+ len = priv->iowins[i].len;
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+ vma->vm_page_prot = phys_mem_access_prot(file, base, len,
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+ vma->vm_page_prot);
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+ if (remap_pfn_range(vma, offset,
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+ base, len,
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+ vma->vm_page_prot))
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+ break;
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+ offset += len;
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+ }
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+
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+ if (i < priv->nr_wins)
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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 rpi_gpiomem_fops = {
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+ .owner = THIS_MODULE,
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+ .open = rpi_gpiomem_open,
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+ .release = rpi_gpiomem_release,
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+ .mmap = rpi_gpiomem_mmap,
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+};
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+
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+static const struct of_device_id rpi_gpiomem_of_match[];
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+
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+static int rpi_gpiomem_probe(struct platform_device *pdev)
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+{
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+ int err, i;
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+ const struct of_device_id *id;
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+ struct device *dev = &pdev->dev;
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+ struct device_node *node = dev->of_node;
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+ struct resource *ioresource;
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+ struct rpi_gpiomem_priv *priv;
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+
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+ /* Allocate buffers and instance data */
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+
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+ priv = kzalloc(sizeof(struct rpi_gpiomem_priv), GFP_KERNEL);
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+
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+ if (!priv) {
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+ err = -ENOMEM;
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+ goto failed_inst_alloc;
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+ }
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+ platform_set_drvdata(pdev, priv);
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+
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+ priv->dev = dev;
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+ id = of_match_device(rpi_gpiomem_of_match, dev);
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+ if (!id)
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+ return -EINVAL;
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+
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+ /*
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+ * Device node naming - for legacy (bcm2835) DT bindings, the driver
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+ * created the node based on a hardcoded name - for new bindings,
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+ * take the node name from DT.
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+ */
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+ if (id == &rpi_gpiomem_of_match[0]) {
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+ priv->name = "gpiomem";
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+ } else {
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+ err = of_property_read_string(node, "chardev-name", &priv->name);
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+ if (err)
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+ return -EINVAL;
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+ }
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+
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+ /*
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+ * Go find the register ranges associated with this instance
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+ */
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+ for (i = 0; i < MAX_RANGES; i++) {
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+ ioresource = platform_get_resource(pdev, IORESOURCE_MEM, i);
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+ if (!ioresource && i == 0) {
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+ dev_err(priv->dev, "failed to get IO resource - no ranges available\n");
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+ err = -ENOENT;
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+ goto failed_get_resource;
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+ }
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+ if (!ioresource)
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+ break;
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+
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+ priv->iowins[i].phys_base = ioresource->start;
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+ priv->iowins[i].len = (ioresource->end + 1) - ioresource->start;
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+ dev_info(&pdev->dev, "window base 0x%08lx size 0x%08lx\n",
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+ priv->iowins[i].phys_base, priv->iowins[i].len);
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+ priv->nr_wins++;
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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(&priv->devid,
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+ DEVICE_MINOR, 1, priv->name);
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+ if (err != 0) {
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+ dev_err(priv->dev, "unable to allocate device number");
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+ goto failed_alloc_chrdev;
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+ }
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+ cdev_init(&priv->rpi_gpiomem_cdev, &rpi_gpiomem_fops);
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+ priv->rpi_gpiomem_cdev.owner = THIS_MODULE;
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+ err = cdev_add(&priv->rpi_gpiomem_cdev, priv->devid, 1);
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+ if (err != 0) {
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+ dev_err(priv->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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+ priv->class = class_create(THIS_MODULE, priv->name);
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+ if (IS_ERR(priv->class)) {
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+ err = PTR_ERR(priv->class);
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+ goto failed_class_create;
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+ }
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+
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+ dev = device_create(priv->class, NULL, priv->devid, NULL, priv->name);
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+ if (IS_ERR(dev)) {
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+ err = PTR_ERR(dev);
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+ goto failed_device_create;
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+ }
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+
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+ dev_info(priv->dev, "initialised %u regions as /dev/%s\n",
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+ priv->nr_wins, priv->name);
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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(priv->class);
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+failed_class_create:
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+ cdev_del(&priv->rpi_gpiomem_cdev);
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+failed_cdev_add:
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+ unregister_chrdev_region(priv->devid, 1);
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+failed_alloc_chrdev:
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+failed_get_resource:
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+ kfree(priv);
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+failed_inst_alloc:
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+ dev_err(&pdev->dev, "could not load rpi_gpiomem");
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+ return err;
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+}
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+
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+static int rpi_gpiomem_remove(struct platform_device *pdev)
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+{
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+ struct device *dev = &pdev->dev;
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+ struct rpi_gpiomem_priv *priv = platform_get_drvdata(pdev);
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+
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+ device_destroy(priv->class, priv->devid);
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+ class_destroy(priv->class);
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+ cdev_del(&priv->rpi_gpiomem_cdev);
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+ unregister_chrdev_region(priv->devid, 1);
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+ kfree(priv);
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+
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+ dev_info(dev, "%s driver removed - OK", priv->name);
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+ return 0;
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+}
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+
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+static const struct of_device_id rpi_gpiomem_of_match[] = {
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+ {
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+ .compatible = "brcm,bcm2835-gpiomem",
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+ },
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+ {
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+ .compatible = "raspberrypi,gpiomem",
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+ },
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+ { /* sentinel */ },
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+};
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+
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+MODULE_DEVICE_TABLE(of, rpi_gpiomem_of_match);
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+
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+static struct platform_driver rpi_gpiomem_driver = {
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+ .probe = rpi_gpiomem_probe,
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+ .remove = rpi_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 = rpi_gpiomem_of_match,
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+ },
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+};
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+
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+module_platform_driver(rpi_gpiomem_driver);
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+
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+MODULE_ALIAS("platform:rpi-gpiomem");
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+MODULE_LICENSE("Dual BSD/GPL");
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+MODULE_DESCRIPTION("Driver for accessing GPIOs from userspace");
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+MODULE_AUTHOR("Jonathan Bell <jonathan@raspberrypi.com>");
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