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ELD (EDID-Like Data) describes to the HDMI/DP audio driver the audio capabilities of the plugged monitor. This adds drm_edid_to_eld() for converting EDID to ELD. The converted ELD will be saved in a new drm_connector.eld[128] data field. This is necessary because the graphics driver will need to fixup some of the data fields (eg. HDMI/DP connection type, AV sync delay) before writing to the hardware ELD buffer. drm_av_sync_delay() will help the graphics drivers dynamically compute the AV sync delay for fixing-up the ELD. ELD selection policy: it's possible for one encoder to be associated with multiple connectors (ie. monitors), in which case the first found ELD will be returned by drm_select_eld(). This policy may not be suitable for all users, but let's start it simple first. The impact of ELD selection policy: assume there are two monitors, one supports stereo playback and the other has 8-channel output; cloned display mode is used, so that the two monitors are associated with the same internal encoder. If only the stereo playback capability is reported, the user won't be able to start 8-channel playback; if the 8-channel ELD is reported, then user space applications may send 8-channel samples down, however the user may actually be listening to the 2-channel monitor and not connecting speakers to the 8-channel monitor. According to James, many TVs will either refuse the display anything or pop-up an OSD warning whenever they receive hdmi audio which they cannot handle. Eventually we will require configurability and/or per-monitor audio control even when the video is cloned. CC: Zhao Yakui <yakui.zhao@intel.com> CC: Wang Zhenyu <zhenyu.z.wang@intel.com> CC: Jeremy Bush <contractfrombelow@gmail.com> CC: Christopher White <c.white@pulseforce.com> CC: Pierre-Louis Bossart <pierre-louis.bossart@intel.com> CC: Paul Menzel <paulepanter@users.sourceforge.net> CC: James Cloos <cloos@jhcloos.com> CC: Chris Wilson <chris@chris-wilson.co.uk> Signed-off-by: Ben Skeggs <bskeggs@redhat.com> Signed-off-by: Wu Fengguang <fengguang.wu@intel.com> Signed-off-by: Keith Packard <keithp@keithp.com> |
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