linux-kernel - Re: [PATCH] gpio/sysfs: Add ID parameter for GPIO lines

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Date:	Tue, 26 Jan 2016 11:25:20 +0100
From:	Ricardo Ribalda Delgado <ricardo.ribalda@...il.com>
To:	Alexandre Courbot <gnurou@...il.com>,
	LKML <linux-kernel@...r.kernel.org>,
	"linux-gpio@...r.kernel.org" <linux-gpio@...r.kernel.org>
Cc:	Ricardo Ribalda Delgado <ricardo.ribalda@...il.com>
Subject: Re: [PATCH] gpio/sysfs: Add ID parameter for GPIO lines

Hello!

Any comment on this?


Thanks!

On Thu, Dec 17, 2015 at 5:48 PM, Ricardo Ribalda Delgado
<ricardo.ribalda@...il.com> wrote:
> On named GPIOs there is currently no find out their numerical id.
>
> Because of this, a GPIO pin named like:
> /sys/class/gpio/PROG_B
>
> cannot be unexported by an application different than the one that
> exported it.
>
> This patch adds a new parameter to the GPIO line called id, that
> shows the numerical id of a given GPIO. E.g.:
>
> $ cat /sys/class/gpio/PROG_B/id
> 496
> $ echo 496 > unexport
>
> Signed-off-by: Ricardo Ribalda Delgado <ricardo.ribalda@...il.com>
> ---
>  Documentation/ABI/testing/sysfs-gpio |  1 +
>  Documentation/gpio/sysfs.txt         |  3 +++
>  drivers/gpio/gpiolib-sysfs.c         | 10 ++++++++++
>  3 files changed, 14 insertions(+)
>
> diff --git a/Documentation/ABI/testing/sysfs-gpio b/Documentation/ABI/testing/sysfs-gpio
> index 55ffa2df1c10..53d78abef4f3 100644
> --- a/Documentation/ABI/testing/sysfs-gpio
> +++ b/Documentation/ABI/testing/sysfs-gpio
> @@ -21,6 +21,7 @@ Description:
>             /value ... always readable, writes fail for input GPIOs
>             /direction ... r/w as: in, out (default low); write: high, low
>             /edge ... r/w as: none, falling, rising, both
> +           /id ... r only, GPIO number
>         /gpiochipN ... for each gpiochip; #N is its first GPIO
>             /base ... (r/o) same as N
>             /label ... (r/o) descriptive, not necessarily unique
> diff --git a/Documentation/gpio/sysfs.txt b/Documentation/gpio/sysfs.txt
> index aeab01aa4d00..68e1b16e747b 100644
> --- a/Documentation/gpio/sysfs.txt
> +++ b/Documentation/gpio/sysfs.txt
> @@ -96,6 +96,9 @@ and have the following read/write attributes:
>                 for "rising" and "falling" edges will follow this
>                 setting.
>
> +       "id" ... ID used for export/unxexport the GPIO. This value may
> +               be used by named GPIOs, to find out their numerical id.
> +
>  GPIO controllers have paths like /sys/class/gpio/gpiochip42/ (for the
>  controller implementing GPIOs starting at #42) and have the following
>  read-only attributes:
> diff --git a/drivers/gpio/gpiolib-sysfs.c b/drivers/gpio/gpiolib-sysfs.c
> index b57ed8e55ab5..3fc5c7231aae 100644
> --- a/drivers/gpio/gpiolib-sysfs.c
> +++ b/drivers/gpio/gpiolib-sysfs.c
> @@ -350,6 +350,15 @@ static ssize_t active_low_store(struct device *dev,
>  }
>  static DEVICE_ATTR_RW(active_low);
>
> +static ssize_t id_show(struct device *dev,
> +               struct device_attribute *attr, char *buf)
> +{
> +       struct gpiod_data *data = dev_get_drvdata(dev);
> +
> +       return  sprintf(buf, "%d\n", desc_to_gpio(data->desc));
> +}
> +static DEVICE_ATTR_RO(id);
> +
>  static umode_t gpio_is_visible(struct kobject *kobj, struct attribute *attr,
>                                int n)
>  {
> @@ -377,6 +386,7 @@ static struct attribute *gpio_attrs[] = {
>         &dev_attr_edge.attr,
>         &dev_attr_value.attr,
>         &dev_attr_active_low.attr,
> +       &dev_attr_id.attr,
>         NULL,
>  };
>
> --
> 2.6.4
>



-- 
Ricardo Ribalda