On Fri, 11 Oct 2019, Sean Paul <sean@xxxxxxxxxx> wrote: > On Thu, Oct 10, 2019 at 04:35:56PM +0300, Jani Nikula wrote: >> On Thu, 10 Oct 2019, Hans de Goede <hdegoede@xxxxxxxxxx> wrote: >> > Hi Jani, >> > >> > During plumbers I had some discussions with Daniel about supporting >> > OLED screens. Userspace may need to know that a panel is OLED for 2 >> > reasons: >> > >> > 1) To avoid screen burn-in >> > 2) OLED screens do not have a classic backlight, so in some cases >> > some sort of brightness/contrast emulation through gamma tables may >> > be necessary to still allow the user to control the brightness. >> >> I'd think most OLED displays have a native way to control >> brightness. Some eDP panels can use the eDP PWM pin to control >> brightness, although it does not directly drive an actual backlight, and >> some others use the eDP standard DPCD brightness control >> methods. Similarly, OLED DSI displays have DCS commands for this. >> >> Often I've seen various content adaptive brightness settings combined >> with the OLED brightness control, so it can be more power efficient than >> using gamma. >> >> > The idea we've discussed is to add a property on the drm_connector >> > (details to be filled in) which indicates that the panel is an OLED >> > panel. >> > >> > This has lead to the question: "how do we know the panel is OLED"? >> > >> > Do you know if this info is coded into the VBT somewhere? >> >> Not AFAICT. But there is the indication of the brightness control >> method, and one option is the eDP AUX interface. I fathom it's entirely >> possible for panels to use the eDP AUX interface for controlling an LCD >> backlight, so this does not directly translate to OLED. >> >> However, the DisplayID spec has Display Device Data block (0x0c) that >> contains Display Device Technology byte, including a value for Organic >> LED/OEL. I haven't actually checked any OLED displays if they have this >> or not, and we don't currently parse it in drm, but this seems like a >> better option than VBT. Moreover, this is usable also for regular DP, >> which should be as important as eDP for the burn-in avoidance. > > One datapoint: I have an eDP OLED panel and it does not seem to have > DisplayID extensions. Does the DPCD say it supports backlight control through DP AUX? BR, Jani. > > Sean > >> >> BR, >> Jani. >> >> >> -- >> Jani Nikula, Intel Open Source Graphics Center -- Jani Nikula, Intel Open Source Graphics Center _______________________________________________ Intel-gfx mailing list Intel-gfx@xxxxxxxxxxxxxxxxxxxxx https://lists.freedesktop.org/mailman/listinfo/intel-gfx
