On Thu, Aug 20, 2015 at 04:43:32PM +0200, Jacek Anaszewski wrote:
> led_set_brightness_sync function was visible only internally to the
> LED subsystem. It is now being made publicly available since it has
> become apparent that this is a caller who should decide whether
> brightness is to be set in a synchronous or an asynchronous way.
>
> The function is modified to use brightness_set_blocking or
> brightness_set op, depending on which of them is implemented, in case
> brightness_set_sync op wasn't been provided.
>
> Signed-off-by: Jacek Anaszewski <j.anaszewski@xxxxxxxxxxx>
> Cc: Andrew Lunn <andrew@xxxxxxx>
> Cc: Sakari Ailus <sakari.ailus@xxxxxxxxxxxxxxx>
> Cc: Pavel Machek <pavel@xxxxxx>
> Cc: Stas Sergeev <stsp@xxxxxxxxxxxxxxxxxxxxx>
> ---
> drivers/leds/led-core.c | 25 +++++++++++++++++++++++++
> drivers/leds/leds.h | 13 -------------
> include/linux/leds.h | 15 +++++++++++++++
> 3 files changed, 40 insertions(+), 13 deletions(-)
>
> diff --git a/drivers/leds/led-core.c b/drivers/leds/led-core.c
> index 549de7e..3f3b71d 100644
> --- a/drivers/leds/led-core.c
> +++ b/drivers/leds/led-core.c
> @@ -141,6 +141,31 @@ void led_set_brightness(struct led_classdev *led_cdev,
> }
> EXPORT_SYMBOL(led_set_brightness);
>
> +int led_set_brightness_sync(struct led_classdev *led_cdev,
> + enum led_brightness value)
> +{
> + int ret = 0;
> +
> + led_cdev->brightness = min(value, led_cdev->max_brightness);
> +
> + if (led_cdev->flags & LED_SUSPENDED)
> + return 0;
> +
> + if (led_cdev->brightness_set_sync)
> + ret = led_cdev->brightness_set_sync(led_cdev,
> + led_cdev->brightness);
> + else if (led_cdev->brightness_set_blocking)
> + led_cdev->brightness_set_blocking(led_cdev,
> + led_cdev->brightness);
> + else if (led_cdev->brightness_set)
> + led_cdev->brightness_set(led_cdev, led_cdev->brightness);
I don't see how this can be correct, when you say:
> +/**
> + * led_set_brightness_sync - set LED brightness synchronously
> + * @led_cdev: the LED to set
> + * @brightness: the brightness to set it to
> + *
> + * Set an LED's brightness immediately. This function will block
> + * the caller for the time required for accessing device register,
> + * and it can sleep.
led_cdev->brightness_set_sync() is fine, it is defined to the
synchronous.
led_cdev->brightness_set_blocking() is O.K.
But led_cdev->brightness_set() only guarantees:
/* Set LED brightness level */
/* Must not sleep, use a workqueue if needed */
void (*brightness_set)(struct led_classdev *led_cdev,
enum led_brightness brightness);
and it seems like 50% of the current drivers use work queues. It has
never been defined to by synchronous. If brightness_set() is your only
choice, you should return -ENOSUP.
With time, you could review all the drivers and move those that are
synchronous to brightness_set_sync().
Andrew
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