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Message-ID: <4CA76BAA.7020507@metafoo.de>
Date: Sat, 02 Oct 2010 19:28:10 +0200
From: Lars-Peter Clausen <lars@...afoo.de>
To: Janusz Krzysztofik <jkrzyszt@....icnet.pl>
CC: Richard Purdie <rpurdie@...ys.net>,
"linux-fbdev@...r.kernel.org" <linux-fbdev@...r.kernel.org>,
linux-kernel@...r.kernel.org, e3-hacking@...th.li
Subject: Re: [RESEND #2][PATCH] LEDS: Add output invertion option to backlight
trigger
Janusz Krzysztofik wrote:
> This patch extends the LED backlight tirgger driver with an option that allows
> for inverting the trigger output polarity.
>
> Whith 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 its display was blanked or it was turned off, without
> touching it.
>
> The invert sysfs control is modeled after a similiar function provided by the
> gpio trigger driver.
>
> Created and tested against linux-2.6.35-rc3 on Amstrad Delta.
> Re-tested against linux-2.6.36-rc5.
>
> Signed-off-by: Janusz Krzysztofik <jkrzyszt@....icnet.pl>
> ---
> drivers/leds/ledtrig-backlight.c | 59 ++++++++++++++++++++++++++++++++++++---
> 1 file changed, 55 insertions(+), 4 deletions(-)
>
> diff -uprN git/drivers/leds/ledtrig-backlight.c git/drivers/leds/ledtrig-backlight.c
> --- git/drivers/leds/ledtrig-backlight.c 2010-06-15 18:01:50.000000000 +0200
> +++ git/drivers/leds/ledtrig-backlight.c 2010-06-23 02:48:44.000000000 +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,
> @@ -39,13 +40,15 @@ static int fb_notifier_callback(struct n
>
> switch (event) {
> case FB_EVENT_BLANK :
> - if (*blank && n->old_status == UNBLANK) {
> + if ((!n->invert && *blank && n->old_status == UNBLANK) ||
> + (n->invert && !*blank && n->old_status == BLANK)) {
> n->brightness = led->brightness;
> led_set_brightness(led, LED_OFF);
> - n->old_status = BLANK;
> - } else if (!*blank && n->old_status == BLANK) {
> + n->old_status = n->invert ? UNBLANK : BLANK;
> + } else if ((!n->invert && !*blank && n->old_status == BLANK) ||
> + (n->invert && *blank && n->old_status == UNBLANK)) {
> led_set_brightness(led, n->brightness);
> - n->old_status = UNBLANK;
> + n->old_status = n->invert ? BLANK : UNBLANK;
> }
> break;
> }
How about some like:
unsigned new_status = *blank ? BLANK : UNBLANK;
if (new_status != n->old_status) {
if ((new_status ^ n->invert) == BLANK) {
n->brightness = led->brightness;
led_set_brightness(led, LED_OFF);
} else {
led_set_brightness(led, n->brightness);
}
n->old_status = new_status;
}
In my opinion that would be more readable.
> @@ -53,6 +56,43 @@ static int fb_notifier_callback(struct n
> 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->invert && n->old_status == UNBLANK) ||
> + (n->invert && n->old_status == BLANK))
> + led_set_brightness(led, n->brightness);
> + else if ((!n->invert && n->old_status == BLANK) ||
> + (n->invert && n->old_status == UNBLANK))
> + led_set_brightness(led, LED_OFF);
> +
> + return num;
> +}
Same here:
if ((n->old_status ^ n->invert) == BLANK)
led_set_brightness(led, LED_OFF);
else
led_set_brightness(led, n->brightness);
> +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 +106,10 @@ 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 +118,12 @@ 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 +132,7 @@ 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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