The patch titled backlight: add low threshold to pwm backlight has been added to the -mm tree. Its filename is backlight-add-low-threshold-to-pwm-backlight.patch Before you just go and hit "reply", please: a) Consider who else should be cc'ed b) Prefer to cc a suitable mailing list as well c) Ideally: find the original patch on the mailing list and do a reply-to-all to that, adding suitable additional cc's *** Remember to use Documentation/SubmitChecklist when testing your code *** See http://userweb.kernel.org/~akpm/stuff/added-to-mm.txt to find out what to do about this The current -mm tree may be found at http://userweb.kernel.org/~akpm/mmotm/ ------------------------------------------------------ Subject: backlight: add low threshold to pwm backlight From: Arun Murthy <arun.murthy@xxxxxxxxxxxxxx> The intensity of the backlight can be varied from a range of max_brightness to zero. Though most, if not all the pwm based backlight devices start flickering at lower brightness value. And also for each device there exists a brightness value below which the backlight appears to be turned off though the value is not equal to zero. If the range of brightness for a device is from zero to max_brightness. A graph is plotted for brightness Vs intensity for the pwm based backlight device has to be a linear graph. intensity | / | / | / |/ --------- 0 max_brightness But pratically on measuring the above we note that the intensity of backlight goes to zero(OFF) when the value in not zero almost nearing to zero(some x%). so the graph looks like intensity | / | / | / | | ------------ 0 x max_brightness In order to overcome this drawback knowing this x% i.e nothing but the low threshold beyond which the backlight is off and will have no effect, the brightness value is being offset by the low threshold value(retaining the linearity of the graph). Now the graph becomes intensity | / | / | / | / ------------- 0 max_brightness With this for each and every digit increment in the brightness from zero there is a change in the intensity of backlight. Devices having this behaviour can set the low threshold brightness(lth_brightness) and pass the same as platform data else can have it as zero. Signed-off-by: Arun Murthy <arun.murthy@xxxxxxxxxxxxxx> Acked-by: Linus Walleij <linus.walleij@xxxxxxxxxxxxxx> Cc: Richard Purdie <rpurdie@xxxxxxxxx> Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> --- drivers/video/backlight/pwm_bl.c | 7 ++++++- include/linux/pwm_backlight.h | 1 + 2 files changed, 7 insertions(+), 1 deletion(-) diff -puN drivers/video/backlight/pwm_bl.c~backlight-add-low-threshold-to-pwm-backlight drivers/video/backlight/pwm_bl.c --- a/drivers/video/backlight/pwm_bl.c~backlight-add-low-threshold-to-pwm-backlight +++ a/drivers/video/backlight/pwm_bl.c @@ -25,6 +25,7 @@ struct pwm_bl_data { struct pwm_device *pwm; struct device *dev; unsigned int period; + unsigned int lth_brightness; int (*notify)(struct device *, int brightness); }; @@ -48,7 +49,9 @@ static int pwm_backlight_update_status(s pwm_config(pb->pwm, 0, pb->period); pwm_disable(pb->pwm); } else { - pwm_config(pb->pwm, brightness * pb->period / max, pb->period); + brightness = pb->lth_brightness + + (brightness * (pb->period - pb->lth_brightness)/ max); + pwm_config(pb->pwm, brightness, pb->period); pwm_enable(pb->pwm); } return 0; @@ -92,6 +95,8 @@ static int pwm_backlight_probe(struct pl pb->period = data->pwm_period_ns; pb->notify = data->notify; + pb->lth_brightness = data->lth_brightness * + (data->pwm_period_ns / data->max_brightness); pb->dev = &pdev->dev; pb->pwm = pwm_request(data->pwm_id, "backlight"); diff -puN include/linux/pwm_backlight.h~backlight-add-low-threshold-to-pwm-backlight include/linux/pwm_backlight.h --- a/include/linux/pwm_backlight.h~backlight-add-low-threshold-to-pwm-backlight +++ a/include/linux/pwm_backlight.h @@ -8,6 +8,7 @@ struct platform_pwm_backlight_data { int pwm_id; unsigned int max_brightness; unsigned int dft_brightness; + unsigned int lth_brightness; unsigned int pwm_period_ns; int (*init)(struct device *dev); int (*notify)(struct device *dev, int brightness); _ Patches currently in -mm which might be from arun.murthy@xxxxxxxxxxxxxx are linux-next.patch backlight-add-low-threshold-to-pwm-backlight.patch -- To unsubscribe from this list: send the line "unsubscribe mm-commits" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html