Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752761Ab3JWIvj (ORCPT ); Wed, 23 Oct 2013 04:51:39 -0400 Received: from mail-la0-f54.google.com ([209.85.215.54]:41615 "EHLO mail-la0-f54.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752685Ab3JWIvf (ORCPT ); Wed, 23 Oct 2013 04:51:35 -0400 Date: Wed, 23 Oct 2013 10:51:28 +0200 From: Johan Hovold To: Jingoo Han Cc: "'Johan Hovold'" , "'Richard Purdie'" , "'Nicolas Ferre'" , linux-fbdev@vger.kernel.org, linux-kernel@vger.kernel.org, stable@vger.kernel.org Subject: Re: [PATCH 1/9] backlight: atmel-pwm-bl: fix reported brightness Message-ID: <20131023085128.GA11025@localhost> References: <1382462819-28576-1-git-send-email-jhovold@gmail.com> <1382462819-28576-2-git-send-email-jhovold@gmail.com> <001901cecf8e$21764db0$6462e910$%han@samsung.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <001901cecf8e$21764db0$6462e910$%han@samsung.com> User-Agent: Mutt/1.5.21 (2010-09-15) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 3176 Lines: 89 On Wed, Oct 23, 2013 at 10:20:59AM +0900, Jingoo Han wrote: > On Wednesday, October 23, 2013 2:27 AM, Johan Hovold wrote: > > > > The driver supports 16-bit brightness values, but the value returned > > from get_brightness was truncated to eight bits. > > > > Cc: stable@vger.kernel.org > > Signed-off-by: Johan Hovold > > --- > > drivers/video/backlight/atmel-pwm-bl.c | 4 ++-- > > 1 file changed, 2 insertions(+), 2 deletions(-) > > > > diff --git a/drivers/video/backlight/atmel-pwm-bl.c b/drivers/video/backlight/atmel-pwm-bl.c > > index 66885fb..8aac273 100644 > > --- a/drivers/video/backlight/atmel-pwm-bl.c > > +++ b/drivers/video/backlight/atmel-pwm-bl.c > > @@ -70,7 +70,7 @@ static int atmel_pwm_bl_set_intensity(struct backlight_device *bd) > > static int atmel_pwm_bl_get_intensity(struct backlight_device *bd) > > { > > struct atmel_pwm_bl *pwmbl = bl_get_data(bd); > > - u8 intensity; > > + u32 intensity; > > > > if (pwmbl->pdata->pwm_active_low) { > > intensity = pwm_channel_readl(&pwmbl->pwmc, PWM_CDTY) - > > @@ -80,7 +80,7 @@ static int atmel_pwm_bl_get_intensity(struct backlight_device *bd) > > pwm_channel_readl(&pwmbl->pwmc, PWM_CDTY); > > } > > > > - return intensity; > > + return (u16)intensity; > > However, atmel_pwm_bl_get_intensity() should return 'int', > instead of 'u16'. Yes, but the cast to int is implicit. Perhaps return (intensity & 0xffff); (or just a comment) would make it more clear why the cast is there. > Also, pwm_channel_readl() returns 'u32'. Yes, (and only the 16 least-significant bits are used). That and the fact that the platform-data limits are currently unsigned long (I was considering fixing this later) was why I preferred keeping all register value manipulation in u32 and do a single cast at the end. > Then, how about the following? > > --- a/drivers/video/backlight/atmel-pwm-bl.c > +++ b/drivers/video/backlight/atmel-pwm-bl.c > @@ -70,17 +70,17 @@ static int atmel_pwm_bl_set_intensity(struct backlight_device *bd) > static int atmel_pwm_bl_get_intensity(struct backlight_device *bd) > { > struct atmel_pwm_bl *pwmbl = bl_get_data(bd); > - u8 intensity; > + u16 intensity; > > if (pwmbl->pdata->pwm_active_low) { > - intensity = pwm_channel_readl(&pwmbl->pwmc, PWM_CDTY) - > + intensity = (u16) pwm_channel_readl(&pwmbl->pwmc, PWM_CDTY) - > pwmbl->pdata->pwm_duty_min; This would actually introduce a new conversion warning (unless you add parentheses as well) as pwm_duty_min is unsigned long. Same below. > } else { > - intensity = pwmbl->pdata->pwm_duty_max - > + intensity = (u16) pwmbl->pdata->pwm_duty_max - > pwm_channel_readl(&pwmbl->pwmc, PWM_CDTY); > } > > - return intensity; > + return (int)intensity; > } However, if you feel strongly about this, I'll respin the series (a later patch would likely no longer apply), use u16 and add casts to the two assignments. Thanks, Johan -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/