Due to inconsistency of how various legacy drivers implemented DPMS the DPMS uabi has a lot of quirks. Atomic standardizes this, but drivers using the DPMS support can't rely on that since legacy drivers still exist.
Laurent asked for this. v2: Improve commit message and explain that DPMS doesn't really exist for the atomic ioctl (it's "ACTIVE" on the CRTC instead). Text polish from Eric's review. Cc: Laurent Pinchart <laurent.pinchart+rene...@ideasonboard.com> Signed-off-by: Daniel Vetter <daniel.vet...@intel.com> Cc: Daniel Vetter <daniel.vet...@intel.com> Cc: Jani Nikula <jani.nik...@linux.intel.com> Cc: Sean Paul <seanp...@chromium.org> Cc: David Airlie <airl...@linux.ie> Cc: Eric Anholt <e...@anholt.net> Reviewed-by: Eric Anholt <e...@anholt.net> --- drivers/gpu/drm/drm_connector.c | 23 +++++++++++++++++++++++ 1 file changed, 23 insertions(+) diff --git a/drivers/gpu/drm/drm_connector.c b/drivers/gpu/drm/drm_connector.c index bb2e60f5feb6..d8ca526ca4ee 100644 --- a/drivers/gpu/drm/drm_connector.c +++ b/drivers/gpu/drm/drm_connector.c @@ -719,6 +719,29 @@ DRM_ENUM_NAME_FN(drm_get_tv_subconnector_name, * callback. For atomic drivers the remapping to the "ACTIVE" property is * implemented in the DRM core. This is the only standard connector * property that userspace can change. + * + * Note that this property cannot be set through the MODE_ATOMIC ioctl, + * userspace must use "ACTIVE" on the CRTC instead. + * + * WARNING: + * + * For userspace also running on legacy drivers the "DPMS" semantics are a + * lot more complicated. First, userspace cannot rely on the "DPMS" value + * returned by the GETCONNECTOR actually reflecting reality, because many + * drivers fail to update it. For atomic drivers this is taken care of in + * drm_atomic_helper_update_legacy_modeset_state(). + * + * The second issue is that the DPMS state is only well-defined when the + * connector is connected to a CRTC. In atomic the DRM core enforces that + * "ACTIVE" is off in such a case, no such checks exists for "DPMS". + * + * Finally, when enabling an output using the legacy SETCONFIG ioctl then + * "DPMS" is forced to ON. But see above, that might not be reflected in + * the software value on legacy drivers. + * + * Summarizing: Only set "DPMS" when the connector is known to be enabled, + * assume that a successful SETCONFIG call also sets "DPMS" to on, and + * never read back the value of "DPMS" because it can be incorrect. * PATH: * Connector path property to identify how this sink is physically * connected. Used by DP MST. This should be set by calling -- 2.9.5 _______________________________________________ dri-devel mailing list dri-devel@lists.freedesktop.org https://lists.freedesktop.org/mailman/listinfo/dri-devel
