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SubjectRe: [RESEND #2] [PATCH v2] LEDS: Add output invertion option to backlight trigger
(Trying an alternate address for Richard, and adding Andrew to Cc..)

On Thu, Dec 09, 2010 at 02:41:50PM +0100, Janusz Krzysztofik wrote:
> This patch extends the LED backlight tirgger driver with an option that allows
> for inverting the trigger output polarity.
>
> With the invertion option provided, I (ab)use the backlight trigger for
> driving a LED that indicates LCD display blank condtition on my Amstrad Delta
> videophone. Since the machine has no dedicated power LED, it was not possible
> to distinguish if the display was blanked, or the machine was turned off,
> without touching it.
>
> The invert sysfs control is patterned after a similiar function of the GPIO
> trigger driver.
>
> Created and tested against linux-2.6.36-rc5 on Amstrad Delta.
> Retested on linux-2.6.37-rc4.
>
> Signed-off-by: Janusz Krzysztofik <jkrzyszt@tis.icnet.pl>
> Cc: Richard Purdie <rpurdie@rpsys.net>
> ---
>
> Resent because I still can't see any response received, while yet another
> merge window is going to pass away soon.
>
> Applies cleanly on top of 2.6.37-rc4, so no need for yet another refresh. Only
> tried to clean up the commit message slightly - maybe my English is not good
> enough to bother with, if not the code?
>
> v1 -> v2 changes:
> - improve some conditional expressions to be more readable; thanks to Ralph
> Corderoy (from e3-hacking) and Lars-Peter Clausen for their suggestions,
> - refresh against linux-2.6.36-rc5.
>
> drivers/leds/ledtrig-backlight.c | 60
> ++++++++++++++++++++++++++++++++++++---
> 1 file changed, 56 insertions(+), 4 deletions(-)
>
> diff -upr linux-2.6.36-rc5.orig/drivers/leds/ledtrig-backlight.c linux-2.6.36-rc5/drivers/leds/ledtrig-backlight.c
> --- linux-2.6.36-rc5.orig/drivers/leds/ledtrig-backlight.c 2010-09-24 15:35:13.000000000 +0200
> +++ linux-2.6.36-rc5/drivers/leds/ledtrig-backlight.c 2010-10-03 15:59:49.000000000 +0200
> @@ -26,6 +26,7 @@ struct bl_trig_notifier {
> int brightness;
> int old_status;
> struct notifier_block notifier;
> + unsigned invert;
> };
>
> static int fb_notifier_callback(struct notifier_block *p,
> @@ -36,23 +37,63 @@ static int fb_notifier_callback(struct n
> struct led_classdev *led = n->led;
> struct fb_event *fb_event = data;
> int *blank = fb_event->data;
> + int new_status = *blank ? BLANK : UNBLANK;
>
> switch (event) {
> case FB_EVENT_BLANK :
> - if (*blank && n->old_status == UNBLANK) {
> + if (new_status == n->old_status)
> + break;
> +
> + if ((n->old_status == UNBLANK) ^ n->invert) {
> n->brightness = led->brightness;
> led_set_brightness(led, LED_OFF);
> - n->old_status = BLANK;
> - } else if (!*blank && n->old_status == BLANK) {
> + } else {
> led_set_brightness(led, n->brightness);
> - n->old_status = UNBLANK;
> }
> +
> + n->old_status = new_status;
> +
> break;
> }
>
> return 0;
> }
>
> +static ssize_t bl_trig_invert_show(struct device *dev,
> + struct device_attribute *attr, char *buf)
> +{
> + struct led_classdev *led = dev_get_drvdata(dev);
> + struct bl_trig_notifier *n = led->trigger_data;
> +
> + return sprintf(buf, "%s\n", n->invert ? "yes" : "no");
> +}
> +
> +static ssize_t bl_trig_invert_store(struct device *dev,
> + struct device_attribute *attr, const char *buf, size_t num)
> +{
> + struct led_classdev *led = dev_get_drvdata(dev);
> + struct bl_trig_notifier *n = led->trigger_data;
> + unsigned invert;
> + int ret;
> +
> + ret = sscanf(buf, "%u", &invert);
> + if (ret < 1) {
> + dev_err(dev, "invalid value\n");
> + return -EINVAL;
> + }
> +
> + n->invert = !!invert;
> +
> + /* After inverting, we need to update the LED. */
> + if ((n->old_status == BLANK) ^ n->invert)
> + led_set_brightness(led, LED_OFF);
> + else
> + led_set_brightness(led, n->brightness);
> +
> + return num;
> +}
> +static DEVICE_ATTR(invert, 0644, bl_trig_invert_show, bl_trig_invert_store);
> +
> static void bl_trig_activate(struct led_classdev *led)
> {
> int ret;
> @@ -66,6 +107,10 @@ static void bl_trig_activate(struct led_
> return;
> }
>
> + ret = device_create_file(led->dev, &dev_attr_invert);
> + if (ret)
> + goto err_invert;
> +
> n->led = led;
> n->brightness = led->brightness;
> n->old_status = UNBLANK;
> @@ -74,6 +119,12 @@ static void bl_trig_activate(struct led_
> ret = fb_register_client(&n->notifier);
> if (ret)
> dev_err(led->dev, "unable to register backlight trigger\n");
> +
> + return;
> +
> +err_invert:
> + led->trigger_data = NULL;
> + kfree(n);
> }
>
> static void bl_trig_deactivate(struct led_classdev *led)
> @@ -82,6 +133,7 @@ static void bl_trig_deactivate(struct le
> (struct bl_trig_notifier *) led->trigger_data;
>
> if (n) {
> + device_remove_file(led->dev, &dev_attr_invert);
> fb_unregister_client(&n->notifier);
> kfree(n);
> }
> --
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