linux-kernel - RE: [PATCH 1/2] leds-lm3530: comment correction about the range of brightness

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Message-ID: <2E48302EED53D048A7BA72B0A307FB511FB8D43D09@EXDCVYMBSTM005.EQ1STM.local>
Date:	Fri, 20 Apr 2012 12:24:56 +0200
From:	Shreshtha Kumar SAHU <shreshthakumar.sahu@...ricsson.com>
To:	"Kim, Milo" <Milo.Kim@...com>
Cc:	"linus.walleij@...aro.org" <linus.walleij@...aro.org>,
	Richard Purdie <rpurdie@...ys.net>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Andrew Morton <akpm@...ux-foundation.org>
Subject: RE: [PATCH 1/2] leds-lm3530: comment correction about the range of
 brightness

IMHO it should be hidden inside driver. For example if hardware supports >8 bits for 
brightness then too we scale/map 0-255 to supported range in hardware.

BR
Shreshtha

-----Original Message-----
From: Kim, Milo [mailto:Milo.Kim@...com] 
Sent: Friday, April 20, 2012 2:14 PM
To: Shreshtha Kumar SAHU
Cc: linus.walleij@...aro.org; Richard Purdie; linux-kernel@...r.kernel.org; Andrew Morton
Subject: RE: [PATCH 1/2] leds-lm3530: comment correction about the range of brightness


In the previous patch, max brightness was limited to 127 because only 7 bits are used in the brightness register.

http://git.kernel.org/?p=linux/kernel/git/torvalds/linux.git;a=commit;h=bbe6453204c568723679212f6d0653b92b3d6244

With this patch, 128 ~ 255 is invalid range of brightness, so comment needs to be corrected.
(Even if the brt_val is greater than 127, the brightness will be set as max_brightness - 127)

Thanks & BR
Milo -

> -----Original Message-----
> From: Shreshtha Kumar SAHU [mailto:shreshthakumar.sahu@...ricsson.com]
> Sent: Friday, April 20, 2012 4:29 PM
> To: Kim, Milo
> Cc: linus.walleij@...aro.org; Richard Purdie; linux-
> kernel@...r.kernel.org; Andrew Morton
> Subject: RE: [PATCH 1/2] leds-lm3530: comment correction about the
> range of brightness
> 
> I feel driver should take care of range provided by hardware by
> scaling the value provided by user, instead of limiting the max
> brightness to user.
> 
> For .e.g. here it can be something like this -
>                 err = i2c_smbus_write_byte_data(drvdata->client,
>                                 LM3530_BRT_CTRL_REG, brt_val / 2);
> 
> I am not sure if application really use/check max brightness in before
> calculating/setting new brightness values.
> 
> -----Original Message-----
> From: Kim, Milo [mailto:Milo.Kim@...com]
> Sent: Thursday, April 19, 2012 12:11 PM
> To: Andrew Morton
> Cc: Shreshtha Kumar SAHU; linus.walleij@...aro.org; Richard Purdie;
> linux-kernel@...r.kernel.org
> Subject: [PATCH 1/2] leds-lm3530: comment correction about the range of
> brightness
> 
> max brightness is 127, so the range of brt_val should be from 0 to 127
> 
> Signed-off-by: Milo(Woogyom) Kim <milo.kim@...com>
> ---
>  include/linux/led-lm3530.h |    2 +-
>  1 files changed, 1 insertions(+), 1 deletions(-)
> 
> diff --git a/include/linux/led-lm3530.h b/include/linux/led-lm3530.h
> index eeae6e7..4b13347 100644
> --- a/include/linux/led-lm3530.h
> +++ b/include/linux/led-lm3530.h
> @@ -92,7 +92,7 @@ struct lm3530_pwm_data {
>   * @als2_resistor_sel: internal resistance from ALS2 input to ground
>   * @als_vmin: als input voltage calibrated for max brightness in mV
>   * @als_vmax: als input voltage calibrated for min brightness in mV
> - * @brt_val: brightness value (0-255)
> + * @brt_val: brightness value (0-127)
>   * @pwm_data: PWM control functions (only valid when the mode is PWM)
>   */
>  struct lm3530_platform_data {
> --
> 1.7.4.1
> 
> 
> Best Regards,
> Milo (Woogyom) Kim
> 

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