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Subject[PATCH 3/6 v12] gpio: Add userland device interface to block GPIO
Date
This patch adds a character device interface to the block GPIO system.

Signed-off-by: Roland Stigge <stigge@antcom.de>
---
Documentation/ABI/testing/dev-gpioblock | 34 ++++
drivers/gpio/gpiolib.c | 225 +++++++++++++++++++++++++++++++-
include/linux/gpio.h | 13 +
3 files changed, 271 insertions(+), 1 deletion(-)

--- /dev/null
+++ linux-2.6/Documentation/ABI/testing/dev-gpioblock
@@ -0,0 +1,34 @@
+What: /dev/<gpioblock>
+Date: Nov 2012
+KernelVersion: 3.7
+Contact: Roland Stigge <stigge@antcom.de>
+Description: The /dev/<gpioblock> character device node provides userspace
+ access to GPIO blocks, named exactly as the block, e.g.
+ /dev/block0.
+
+ Reading:
+ When reading sizeof(unsigned long) bytes from the device, the
+ current state of the block, masked by the current mask (see
+ below) can be obtained as a word. When the device is opened
+ with O_NONBLOCK, read() always returns with data immediately,
+ otherwise it blocks until data is available, see IRQ handling
+ below.
+
+ Writing:
+ By writing sizeof(unsigned long) bytes to the device, the
+ current state of the block can be set. This operation is
+ masked by the current mask (see below).
+
+ IRQ handling:
+ When one or more IRQs in the block are IRQ capable, you can
+ poll() on the device to check/wait for this IRQ. If no IRQ
+ is available, poll() returns -ENOSYS and userspace needs to
+ (busy) poll itself if necessary.
+
+ Setting the mask (default: all bits set):
+ By doing an ioctl(fd, 0, &mask) with an unsigned long mask, the
+ current mask for read and write operations on this gpio block
+ can be set.
+
+ See also Documentation/gpio.txt for an explanation of block
+ GPIO.
--- linux-2.6.orig/drivers/gpio/gpiolib.c
+++ linux-2.6/drivers/gpio/gpiolib.c
@@ -11,6 +11,8 @@
#include <linux/of_gpio.h>
#include <linux/idr.h>
#include <linux/slab.h>
+#include <linux/uaccess.h>
+#include <linux/poll.h>

#define CREATE_TRACE_POINTS
#include <trace/events/gpio.h>
@@ -2243,6 +2245,207 @@ struct gpio_block *gpio_block_find_by_na
}
EXPORT_SYMBOL_GPL(gpio_block_find_by_name);

+static struct gpio_block *gpio_block_find_by_minor(int minor)
+{
+ struct gpio_block *i;
+
+ list_for_each_entry(i, &gpio_block_list, list)
+ if (i->miscdev.minor == minor)
+ return i;
+ return NULL;
+}
+
+static bool gpio_block_is_irq_duplicate(struct gpio_block *block, int index)
+{
+ int irq = gpio_to_irq(block->gpio[index]);
+ int i;
+
+ for (i = 0; i < index; i++)
+ if (gpio_to_irq(block->gpio[i]) == irq)
+ return true;
+ return false;
+}
+
+static irqreturn_t gpio_block_irq_handler(int irq, void *dev)
+{
+ struct gpio_block *block = dev;
+
+ wake_up_interruptible(&block->wait_queue);
+ block->got_int = true;
+
+ return IRQ_HANDLED;
+}
+
+static int gpio_block_fop_open(struct inode *in, struct file *f)
+{
+ int i;
+ struct gpio_block *block = gpio_block_find_by_minor(MINOR(in->i_rdev));
+ int status;
+ int irq;
+
+ if (!block)
+ return -ENOENT;
+
+ block->irq_controlled = false;
+ block->got_int = false;
+ spin_lock_init(&block->lock);
+ init_waitqueue_head(&block->wait_queue);
+ f->private_data = block;
+
+ for (i = 0; i < block->ngpio; i++) {
+ status = gpio_request(block->gpio[i], block->name);
+ if (status)
+ goto err1;
+
+ irq = gpio_to_irq(block->gpio[i]);
+ if (irq >= 0 &&
+ !test_bit(FLAG_IS_OUT, &gpio_desc[block->gpio[i]].flags) &&
+ !gpio_block_is_irq_duplicate(block, i)) {
+ status = request_irq(irq, gpio_block_irq_handler,
+ IRQF_SHARED,
+ block->name, block);
+ if (status)
+ goto err2;
+
+ block->irq_controlled = true;
+ }
+ }
+
+ return 0;
+
+err1:
+ while (i > 0) {
+ i--;
+
+ irq = gpio_to_irq(block->gpio[i]);
+ if (irq >= 0 &&
+ !test_bit(FLAG_IS_OUT, &gpio_desc[block->gpio[i]].flags) &&
+ !gpio_block_is_irq_duplicate(block, i))
+ free_irq(irq, block);
+err2:
+ gpio_free(block->gpio[i]);
+ }
+ return status;
+}
+
+static int gpio_block_fop_release(struct inode *in, struct file *f)
+{
+ int i;
+ struct gpio_block *block = (struct gpio_block *)f->private_data;
+
+ for (i = 0; i < block->ngpio; i++) {
+ int irq = gpio_to_irq(block->gpio[i]);
+
+ if (irq >= 0 &&
+ !test_bit(FLAG_IS_OUT, &gpio_desc[block->gpio[i]].flags) &&
+ !gpio_block_is_irq_duplicate(block, i))
+ free_irq(irq, block);
+
+ gpio_free(block->gpio[i]);
+ }
+
+ return 0;
+}
+
+static int got_int(struct gpio_block *block)
+{
+ unsigned long flags;
+ int result;
+
+ spin_lock_irqsave(&block->lock, flags);
+ result = block->got_int;
+ spin_unlock_irqrestore(&block->lock, flags);
+
+ return result;
+}
+
+static ssize_t gpio_block_fop_read(struct file *f, char __user *buf, size_t n,
+ loff_t *offset)
+{
+ struct gpio_block *block = (struct gpio_block *)f->private_data;
+ int err;
+ unsigned long flags;
+
+ if (block->irq_controlled) {
+ if (!(f->f_flags & O_NONBLOCK))
+ wait_event_interruptible(block->wait_queue,
+ got_int(block));
+ spin_lock_irqsave(&block->lock, flags);
+ block->got_int = 0;
+ spin_unlock_irqrestore(&block->lock, flags);
+ }
+
+ if (n >= sizeof(unsigned long)) {
+ unsigned long values = gpio_block_get(block, block->cur_mask);
+
+ err = put_user(values, (unsigned long __user *)buf);
+ if (err)
+ return err;
+
+ return sizeof(unsigned long);
+ }
+ return 0;
+}
+
+static ssize_t gpio_block_fop_write(struct file *f, const char __user *buf,
+ size_t n, loff_t *offset)
+{
+ struct gpio_block *block = (struct gpio_block *)f->private_data;
+ int err;
+
+ if (n >= sizeof(unsigned long)) {
+ unsigned long values;
+
+ err = get_user(values, (unsigned long __user *)buf);
+ if (err)
+ return err;
+ if (gpio_block_is_output(block))
+ gpio_block_set(block, block->cur_mask, values);
+ else
+ return -EPERM;
+ return sizeof(unsigned long);
+ }
+ return 0;
+}
+
+static long gpio_block_fop_ioctl(struct file *f, unsigned int cmd,
+ unsigned long arg)
+{
+ struct gpio_block *block = (struct gpio_block *)f->private_data;
+ unsigned long __user *x = (unsigned long __user *)arg;
+
+ if (cmd == 0)
+ return get_user(block->cur_mask, x);
+
+ return -EINVAL;
+}
+
+static unsigned int gpio_block_fop_poll(struct file *f,
+ struct poll_table_struct *pt)
+{
+ struct gpio_block *block = (struct gpio_block *)f->private_data;
+
+ if (!block->irq_controlled)
+ return -ENOSYS;
+
+ if (!got_int(block))
+ poll_wait(f, &block->wait_queue, pt);
+
+ if (got_int(block))
+ return POLLIN;
+
+ return 0;
+}
+
+static const struct file_operations gpio_block_fops = {
+ .open = gpio_block_fop_open,
+ .release = gpio_block_fop_release,
+ .read = gpio_block_fop_read,
+ .write = gpio_block_fop_write,
+ .unlocked_ioctl = gpio_block_fop_ioctl,
+ .poll = gpio_block_fop_poll,
+};
+
int gpio_block_register(struct gpio_block *block)
{
int ret;
@@ -2253,12 +2456,31 @@ int gpio_block_register(struct gpio_bloc
list_add(&block->list, &gpio_block_list);

ret = gpio_block_export(block);
- if (ret)
+
+ /*
+ * ret == ENOSYS is the case where GPIO_SYSFS is deactivated. In this
+ * case, we can continue safely anyway, since we can provide the device
+ * interface.
+ */
+ if (ret && ret != -ENOSYS)
goto err1;

+ block->miscdev.name = block->name;
+ block->miscdev.nodename = block->name;
+ block->miscdev.minor = MISC_DYNAMIC_MINOR;
+ block->miscdev.fops = &gpio_block_fops;
+ block->miscdev.mode = S_IWUSR | S_IRUGO;
+
+ ret = misc_register(&block->miscdev);
+ if (ret)
+ goto err2;
+
return 0;
+err2:
+ gpio_block_unexport(block);
err1:
list_del(&block->list);
+
return ret;
}
EXPORT_SYMBOL_GPL(gpio_block_register);
@@ -2271,6 +2493,7 @@ void gpio_block_unregister(struct gpio_b
if (i == block) {
list_del(&i->list);
gpio_block_unexport(block);
+ misc_deregister(&block->miscdev);
break;
}
}
--- linux-2.6.orig/include/linux/gpio.h
+++ linux-2.6/include/linux/gpio.h
@@ -4,6 +4,9 @@
#include <linux/errno.h>
#include <linux/types.h>
#include <linux/list.h>
+#include <linux/sched.h>
+#include <linux/miscdevice.h>
+#include <linux/spinlock.h>

/* see Documentation/gpio.txt */

@@ -89,6 +92,11 @@ struct gpio_block_chip {
* @gpio: list of gpios in this block
* @list: global list of blocks, maintained by gpiolib
* @cur_mask: currently used gpio mask used by userspace API
+ * @miscdev: userspace API: device
+ * @wait_queue: userspace API: wait queue waiting for IRQ
+ * @irq_controlled: userspace API: flag: using IRQ or not
+ * @got_int: userspace API: change detection via IRQ
+ * @lock: userspace API: spinlock for IRQ manipulated data
*/
struct gpio_block {
struct list_head gbc_list;
@@ -99,6 +107,11 @@ struct gpio_block {

struct list_head list;
unsigned long cur_mask;
+ struct miscdevice miscdev;
+ wait_queue_head_t wait_queue;
+ bool irq_controlled;
+ bool got_int;
+ spinlock_t lock;
};

#ifdef CONFIG_GENERIC_GPIO

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