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[80.7.220.175]) by smtp.gmail.com with ESMTPSA id h13-20020a5d504d000000b002100e86319asm15031976wrt.78.2022.06.09.02.54.13 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 09 Jun 2022 02:54:14 -0700 (PDT) Date: Thu, 9 Jun 2022 10:54:12 +0100 From: Daniel Thompson To: Stephen Kitt Cc: Nicolas Ferre , Helge Deller , Alexandre Belloni , Claudiu Beznea , linux-fbdev@vger.kernel.org, dri-devel@lists.freedesktop.org, linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH] fbdev: atmel_lcdfb: Rework backlight status updates Message-ID: <20220609095412.fccofr2e2kpzhw4t@maple.lan> References: <20220608205623.2106113-1-steve@sk2.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20220608205623.2106113-1-steve@sk2.org> Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, Jun 08, 2022 at 10:56:23PM +0200, Stephen Kitt wrote: > Instead of checking the state of various backlight_properties fields > against the memorised state in atmel_lcdfb_info.bl_power, > atmel_bl_update_status() should retrieve the desired state using > backlight_get_brightness (which takes into account the power state, > blanking etc.). This means the explicit checks using props.fb_blank > and props.power can be dropped. > > Then brightness can only be negative if the backlight is on but > props.brightness is negative, so the test before reading the > brightness value from the hardware can be simplified to > (brightness < 0). props.brightness should always be in the interval 0..max_brightness. This is enforced by the main backlight code (and APIs to set the brightness use unsigned values). Thus props.brightness could only be negative is the driver explicitly sets a negative value as some kind of placeholder (which this driver does not do). I don't think there is any need to keep this logic. Daniel. > diff --git a/drivers/video/fbdev/atmel_lcdfb.c b/drivers/video/fbdev/atmel_lcdfb.c > index 1fc8de4ecbeb..06159a4da293 100644 > --- a/drivers/video/fbdev/atmel_lcdfb.c > +++ b/drivers/video/fbdev/atmel_lcdfb.c > @@ -109,22 +108,10 @@ static u32 contrast_ctr = ATMEL_LCDC_PS_DIV8 > static int atmel_bl_update_status(struct backlight_device *bl) > { > struct atmel_lcdfb_info *sinfo = bl_get_data(bl); > - int power = sinfo->bl_power; > - int brightness = bl->props.brightness; > + int brightness = backlight_get_brightness(bl); > > - /* REVISIT there may be a meaningful difference between > - * fb_blank and power ... there seem to be some cases > - * this doesn't handle correctly. > - */ > - if (bl->props.fb_blank != sinfo->bl_power) > - power = bl->props.fb_blank; > - else if (bl->props.power != sinfo->bl_power) > - power = bl->props.power; > - > - if (brightness < 0 && power == FB_BLANK_UNBLANK) > + if (brightness < 0) > brightness = lcdc_readl(sinfo, ATMEL_LCDC_CONTRAST_VAL); > - else if (power != FB_BLANK_UNBLANK) > - brightness = 0; > > lcdc_writel(sinfo, ATMEL_LCDC_CONTRAST_VAL, brightness); > if (contrast_ctr & ATMEL_LCDC_POL_POSITIVE)