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Message-ID: <507BA0B4.5030701@gmail.com>
Date: Mon, 15 Oct 2012 16:35:48 +1100
From: Ryan Mallon <rmallon@...il.com>
To: Roland Stigge <stigge@...com.de>
CC: grant.likely@...retlab.ca, linus.walleij@...aro.org,
linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
w.sang@...gutronix.de, jbe@...gutronix.de, plagnioj@...osoft.com,
highguy@...il.com, broonie@...nsource.wolfsonmicro.com
Subject: Re: [PATCH RFC 2/6 v3] gpio: Add sysfs support to block GPIO API
On 13/10/12 06:11, Roland Stigge wrote:
> This patch adds sysfs support to the block GPIO API.
>
> Signed-off-by: Roland Stigge <stigge@...com.de>
Hi Roland,
Some comments below,
~Ryan
>
> ---
> Documentation/ABI/testing/sysfs-gpio | 6
> drivers/gpio/gpiolib.c | 226 ++++++++++++++++++++++++++++++++++-
> include/asm-generic/gpio.h | 11 +
> include/linux/gpio.h | 13 ++
> 4 files changed, 254 insertions(+), 2 deletions(-)
>
> --- linux-2.6.orig/Documentation/ABI/testing/sysfs-gpio
> +++ linux-2.6/Documentation/ABI/testing/sysfs-gpio
> @@ -24,4 +24,8 @@ Description:
> /base ... (r/o) same as N
> /label ... (r/o) descriptive, not necessarily unique
> /ngpio ... (r/o) number of GPIOs; numbered N to N + (ngpio - 1)
> -
> + /blockN ... for each GPIO block #N
> + /ngpio ... (r/o) number of GPIOs in this group
> + /exported ... sysfs export state of this group (0, 1)
> + /value ... current value as 32 or 64 bit integer in decimal
> + (only available if /exported is 1)
> --- linux-2.6.orig/drivers/gpio/gpiolib.c
> +++ linux-2.6/drivers/gpio/gpiolib.c
> @@ -974,6 +974,218 @@ static void gpiochip_unexport(struct gpi
> chip->label, status);
> }
>
> +static ssize_t gpio_block_ngpio_show(struct device *dev,
> + struct device_attribute *attr, char *buf)
> +{
> + const struct gpio_block *block = dev_get_drvdata(dev);
> +
> + return sprintf(buf, "%u\n", block->ngpio);
> +}
> +static struct device_attribute
> +dev_attr_block_ngpio = __ATTR(ngpio, 0444, gpio_block_ngpio_show, NULL);
static DEVICE_ATTR(ngpio, S_IRUGO, gpio_block_ngpio_show, NULL);
> +
> +static ssize_t gpio_block_value_show(struct device *dev,
> + struct device_attribute *attr, char *buf)
> +{
> + const struct gpio_block *block = dev_get_drvdata(dev);
> +
> + return sprintf(buf, "%u\n", gpio_block_get(block));
Printing the value of a bunch of pins as a decimal is a bit odd. Hex, or
a bitmap would be more appropriate.
> +}
> +
> +static bool gpio_block_is_output(struct gpio_block *block)
> +{
> + int i;
> +
> + for (i = 0; i < block->ngpio; i++)
> + if (!test_bit(FLAG_IS_OUT, &gpio_desc[block->gpio[i]].flags))
> + return false;
Shouldn't a block force all of the pins to be the same direction? Or at
least have gpio_block_set skip pins which aren't outputs.
> + return true;
> +}
> +
> +static ssize_t gpio_block_value_store(struct device *dev,
> + struct device_attribute *attr,
> + const char *buf, size_t size)
> +{
> + ssize_t status;
> + struct gpio_block *block = dev_get_drvdata(dev);
> + unsigned long value;
> +
> + mutex_lock(&sysfs_lock);
> +
> + status = kstrtoul(buf, 0, &value);
> + if (status == 0) {
You don't need to do the kstrtoul under the lock:
err = kstrtoul(buf, 0, &value);
if (err)
return err;
mutex_lock(&sysfs_lock);
...
Global lock is a bit lame, it serialises all of your bitbanged busses
against each other. Why is it not part of the gpio_block structure?
> + if (gpio_block_is_output(block)) {
> + gpio_block_set(block, value);
> + status = size;
> + } else {
> + status = -EPERM;
> + }
> + }
> +
> + mutex_unlock(&sysfs_lock);
> + return status;
> +}
> +
> +static struct device_attribute
> +dev_attr_block_value = __ATTR(value, 0644, gpio_block_value_show,
> + gpio_block_value_store);
Use DEVICE_ATTR and S_IWUSR | S_IRUGO permission macros.
> +
> +static int gpio_block_value_is_exported(struct gpio_block *block)
> +{
> + struct device *dev;
> + struct sysfs_dirent *sd = NULL;
> +
> + mutex_lock(&sysfs_lock);
> + dev = class_find_device(&gpio_class, NULL, block, match_export);
> + if (!dev)
> + goto out;
> +
> + sd = sysfs_get_dirent(dev->kobj.sd, NULL, "value");
> +
> +out:
> + mutex_unlock(&sysfs_lock);
> + return sd ? 1 : 0;
return sd;
or:
return !!sd;
> +}
> +
> +static ssize_t gpio_block_exported_show(struct device *dev,
> + struct device_attribute *attr,
> + char *buf)
> +{
> + struct gpio_block *block = dev_get_drvdata(dev);
> +
> + return sprintf(buf, "%u\n", gpio_block_value_is_exported(block));
> +}
> +
> +static int gpio_block_value_export(struct gpio_block *block)
> +{
> + struct device *dev;
> + int status;
> + int i;
> +
> + mutex_lock(&sysfs_lock);
> +
> + for (i = 0; i < block->ngpio; i++) {
> + status = gpio_request(block->gpio[i], "sysfs");
> + if (status)
> + goto out;
> + }
> +
> + dev = class_find_device(&gpio_class, NULL, block, match_export);
> + if (!dev) {
> + status = -ENODEV;
> + goto out;
> + }
> +
> + status = device_create_file(dev, &dev_attr_block_value);
> + if (status)
> + goto out;
> +
> + mutex_unlock(&sysfs_lock);
> + return 0;
> +
> +out:
> + while (i > 0) {
> + i--;
> + gpio_free(block->gpio[i]);
> + }
Nitpick:
while (--i >= 0)
gpio_free(block->gpio[i]);
> +
> + mutex_unlock(&sysfs_lock);
> + return status;
> +}
> +
> +static int gpio_block_value_unexport(struct gpio_block *block)
> +{
> + struct device *dev;
> + int i;
> +
> + dev = class_find_device(&gpio_class, NULL, block, match_export);
> + if (!dev)
> + return -ENODEV;
> +
> + for (i = 0; i < block->ngpio; i++)
> + gpio_free(block->gpio[i]);
> +
> + device_remove_file(dev, &dev_attr_block_value);
> +
> + return 0;
> +}
> +
> +static ssize_t gpio_block_exported_store(struct device *dev,
> + struct device_attribute *attr,
> + const char *buf, size_t size)
> +{
> + long value;
> + int status;
> + struct gpio_block *block = dev_get_drvdata(dev);
> + int exported = gpio_block_value_is_exported(block);
> +
> + status = kstrtoul(buf, 0, &value);
> + if (status < 0)
> + goto err;
> +
> + if (value != exported) {
> + if (value)
> + status = gpio_block_value_export(block);
> + else
> + status = gpio_block_value_unexport(block);
> + if (!status)
> + status = size;
> + } else {
> + status = size;
> + }
> +err:
> + return status;
> +}
> +
> +static DEVICE_ATTR(exported, 0644, gpio_block_exported_show,
> + gpio_block_exported_store);
> +
> +static const struct attribute *gpio_block_attrs[] = {
> + &dev_attr_block_ngpio.attr,
> + &dev_attr_exported.attr,
> + NULL,
> +};
> +
> +static const struct attribute_group gpio_block_attr_group = {
> + .attrs = (struct attribute **) gpio_block_attrs,
> +};
> +
> +int gpio_block_export(struct gpio_block *block)
> +{
> + int status;
> + struct device *dev;
> +
> + /* can't export until sysfs is available ... */
> + if (!gpio_class.p) {
> + pr_debug("%s: called too early!\n", __func__);
> + return -ENOENT;
> + }
> +
> + mutex_lock(&sysfs_lock);
> + dev = device_create(&gpio_class, NULL, MKDEV(0, 0), block,
> + block->name);
> + if (!IS_ERR(dev))
> + status = sysfs_create_group(&dev->kobj, &gpio_block_attr_group);
> + else
> + status = PTR_ERR(dev);
> + mutex_unlock(&sysfs_lock);
> +
> + return status;
> +}
> +EXPORT_SYMBOL_GPL(gpio_block_export);
> +
> +void gpio_block_unexport(struct gpio_block *block)
> +{
> + struct device *dev;
> +
> + mutex_lock(&sysfs_lock);
> + dev = class_find_device(&gpio_class, NULL, block, match_export);
> + if (dev)
> + device_unregister(dev);
> + mutex_unlock(&sysfs_lock);
> +}
> +EXPORT_SYMBOL_GPL(gpio_block_unexport);
> +
> static int __init gpiolib_sysfs_init(void)
> {
> int status;
> @@ -1882,7 +2094,14 @@ int gpio_block_register(struct gpio_bloc
> break;
> }
> }
> - return i == NR_GPIO_BLOCKS ? -EBUSY : 0;
> + if (i == NR_GPIO_BLOCKS)
> + goto err;
> +
> + gpio_block_export(block);
> +
> + return 0;
> +err:
> + return -EBUSY;
> }
> EXPORT_SYMBOL_GPL(gpio_block_register);
>
> @@ -1896,6 +2115,11 @@ void gpio_block_unregister(struct gpio_b
> break;
> }
> }
> +
> + if (i == NR_GPIO_BLOCKS)
> + return;
> +
> + gpio_block_unexport(block);
> }
> EXPORT_SYMBOL_GPL(gpio_block_unregister);
>
> --- linux-2.6.orig/include/asm-generic/gpio.h
> +++ linux-2.6/include/asm-generic/gpio.h
> @@ -210,6 +210,8 @@ extern int gpio_export_link(struct devic
> unsigned gpio);
> extern int gpio_sysfs_set_active_low(unsigned gpio, int value);
> extern void gpio_unexport(unsigned gpio);
> +extern int gpio_block_export(struct gpio_block *block);
> +extern void gpio_block_unexport(struct gpio_block *block);
>
> #endif /* CONFIG_GPIO_SYSFS */
>
> @@ -269,6 +271,15 @@ static inline int gpio_sysfs_set_active_
> static inline void gpio_unexport(unsigned gpio)
> {
> }
> +
> +static inline int gpio_block_export(struct gpio_block *block)
> +{
> + return -ENOSYS;
> +}
> +
> +static inline void gpio_block_unexport(struct gpio_block *block)
> +{
> +}
> #endif /* CONFIG_GPIO_SYSFS */
>
> #endif /* _ASM_GENERIC_GPIO_H */
> --- linux-2.6.orig/include/linux/gpio.h
> +++ linux-2.6/include/linux/gpio.h
> @@ -278,6 +278,19 @@ static inline void gpio_unexport(unsigne
> WARN_ON(1);
> }
>
> +static inline int gpio_block_export(struct gpio_block *block)
> +{
> + /* GPIO block can never have been requested or set as {in,out}put */
> + WARN_ON(1);
> + return -EINVAL;
> +}
> +
> +static inline void gpio_block_unexport(struct gpio_block *block)
> +{
> + /* GPIO block can never have been exported */
> + WARN_ON(1);
> +}
> +
> static inline int gpio_to_irq(unsigned gpio)
> {
> /* GPIO can never have been requested or set as input */
> --
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