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. Sean > > BR, > Jani. > > > -- > Jani Nikula, Intel Open Source Graphics Center -- Sean Paul, Software Engineer, Google / Chromium OS _______________________________________________ Intel-gfx mailing list Intel-gfx@xxxxxxxxxxxxxxxxxxxxx https://lists.freedesktop.org/mailman/listinfo/intel-gfx
