added brightness feature to lcd class.
in [Kernel]
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From: Andrew Morton on 9 Nov 2009 18:30 On Mon, 2 Nov 2009 17:50:02 +0900 InKi Dae <daeinki(a)gmail.com> wrote: > This patch adds brightness feature to lcd class. > (kernel/driver/video/backlight/lcd.c) > > In the past, most of the lcd panels for embedded system was TFT-LCD > Panel needing backlight device. > But now AMOLED LCD Panel appeared so we should consider brightness > control for AMOLED Panel. > > For the time being, I used backlight fake driver for brightness > control of AMOLED LCD Panel. > But this way is not good, so I propose to add brightness feature to lcd class. > > For this, I attached patch file and if my proposal is approved > Then I will send s6e63m0 and tl2796 AMOLED lcd panel driver based on > lcd class modified soon. Please send the s6e63m0 and tl2796 patches anyway. That way we have some examples of how this new capability is used by drivers. -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo(a)vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
From: Richard Purdie on 9 Nov 2009 18:40 On Mon, 2009-11-02 at 17:50 +0900, InKi Dae wrote: > This patch adds brightness feature to lcd class. > (kernel/driver/video/backlight/lcd.c) > > In the past, most of the lcd panels for embedded system was TFT-LCD > Panel needing backlight device. > But now AMOLED LCD Panel appeared so we should consider brightness > control for AMOLED Panel. > > For the time being, I used backlight fake driver for brightness > control of AMOLED LCD Panel. > But this way is not good, so I propose to add brightness feature to lcd class. > > For this, I attached patch file and if my proposal is approved > Then I will send s6e63m0 and tl2796 AMOLED lcd panel driver based on > lcd class modified soon. Pavel has a good point but let me try and explain it differently. The point of the backlight class is to expose a backlight brightness control to userspace in a consistent well defined way. Anyone wishing to write a piece of software to control the brightness of a backlight then only needs to support *one* interface. It is entirely accepted and normal that multiple "class" devices may appear in userspace for one piece of physical hardware. Your patch duplicates a userspace API and means any backlight application would have to look for *two* different interfaces. This is unacceptable. Why can't your driver just register a backlight interface and an LCD interface? I'd imagine your backlight and LCD can be powered on/off separately too. Please also cc: the backlight/lcd maintainer (me) on backlight/lcd patches in future. Andrew: Can you drop that patch from -mm please as I'm not convinced we need two backlight brightness interfaces around... Cheers, Richard -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo(a)vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
From: InKi Dae on 9 Nov 2009 22:30 Thank you for your comments. it is a good idea that lcd driver registers interfaces to lcd class and backlight class. but I think for AMOLED LCD Panel, backlight couldn't be real device so power on/off for backlight device doesn't make sense. I had tried lcd driver registers interfaces to lcd class and backlight class as you said. and also backlight fake driver as Pavel said. but I thought to use my patch is more simple and effective. of course, this patch has a problem that it has different path from backlight class for controlling brightness. how about creating symbolic link file for competiability? Best Regards, InKi Dae. 2009/11/10 Richard Purdie <rpurdie(a)linux.intel.com>: > On Mon, 2009-11-02 at 17:50 +0900, InKi Dae wrote: >> This patch adds brightness feature to lcd class. >> (kernel/driver/video/backlight/lcd.c) >> >> In the past, most of the lcd panels for embedded system was TFT-LCD >> Panel needing backlight device. >> But now AMOLED LCD Panel appeared so we should consider brightness >> control for AMOLED Panel. >> >> For the time being, I used backlight fake driver for brightness >> control of AMOLED LCD Panel. >> But this way is not good, so I propose to add brightness feature to lcd class. >> >> For this, I attached patch file and if my proposal is approved >> Then I will send s6e63m0 and tl2796 AMOLED lcd panel driver based on >> lcd class modified soon. > > Pavel has a good point but let me try and explain it differently. > > The point of the backlight class is to expose a backlight brightness > control to userspace in a consistent well defined way. Anyone wishing to > write a piece of software to control the brightness of a backlight then > only needs to support *one* interface. > > It is entirely accepted and normal that multiple "class" devices may > appear in userspace for one piece of physical hardware. > > Your patch duplicates a userspace API and means any backlight > application would have to look for *two* different interfaces. This is > unacceptable. > > Why can't your driver just register a backlight interface and an LCD > interface? I'd imagine your backlight and LCD can be powered on/off > separately too. > > Please also cc: the backlight/lcd maintainer (me) on backlight/lcd > patches in future. > > Andrew: Can you drop that patch from -mm please as I'm not convinced we > need two backlight brightness interfaces around... > > Cheers, > > Richard > > > > -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo(a)vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
From: Richard Purdie on 10 Nov 2009 03:50 On Tue, 2009-11-10 at 12:26 +0900, InKi Dae wrote: > Thank you for your comments. > > it is a good idea that lcd driver registers interfaces to lcd class > and backlight class. > but I think for AMOLED LCD Panel, backlight couldn't be real device so > power on/off > for backlight device doesn't make sense. The backlight power control can just turn the backlight level down to its lowest setting (off)? > I had tried lcd driver registers interfaces to lcd class and backlight > class as you said. > and also backlight fake driver as Pavel said. So you've tried this, what was the problem? Perhaps post this driver code to illustrate your problem? > but I thought to use my patch is more simple and effective. > of course, this patch has a problem that it has different path from > backlight class > for controlling brightness. > > how about creating symbolic link file for competiability? Creating two ways to do something (with or without symlinks) is not simple and effective for anything other than your driver. Cheers, Richard -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo(a)vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
From: Matthew Garrett on 10 Nov 2009 10:30 Is the confusion here just that LED displays aren't backlit in the traditional sense of the term? -- Matthew Garrett | mjg59(a)srcf.ucam.org -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo(a)vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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