Recent Intel platforms (SKL+) support a background canvas color below the hardware planes. This background color can be seen on areas not covered by a plane, or if we program the hardware with various plane blending modes.
Chandra Konduru previously took a stab at writing i915 patches to support this feature, but we were in the middle of the great i915 atomic transition at the time, so there was too much driver churn to ever get them in. Now that i915 atomic work has settled down a bit, let's make another attempt to get this feature support in.
One of the items that came up in review of Chandra's earlier patches was that although userspace needs to pass a color value to the kernel, it would be best if userspace didn't have to care about the formatting of color values used by the underyling hardware (i.e., number of bits, ordering of R,G,B components, etc.). The first patch here aims to address that by setting up an 'RGBA' property type, specifying a fixed bit layout (with 16bpc), and providing helper macros to fetch specific color bits with the desired precision. This should prevent drivers from trying to shove property values directly into the hardware, which could lead to incompatibility between platforms if we aren't careful.
A libdrm patch that provides helper macros to build color values of the appropriate format will be provided as a followup, as will an update to the i-g-t test for this feature (which is surprisingly already merged, even though the kernel support isn't there yet).
Cc: dri-devel@lists.freedesktop.org Cc: Chandra Konduru chandra.konduru@intel.com
Matt Roper (2): drm: Add infrastructure for CRTC background color property drm/i915/skl: Add support for pipe background color
Documentation/DocBook/gpu.tmpl | 10 +++++++- drivers/gpu/drm/drm_atomic.c | 4 +++ drivers/gpu/drm/drm_crtc.c | 33 ++++++++++++++++++++++++ drivers/gpu/drm/i915/i915_debugfs.c | 9 +++++++ drivers/gpu/drm/i915/i915_reg.h | 10 ++++++++ drivers/gpu/drm/i915/intel_display.c | 43 +++++++++++++++++++++++++++++++ include/drm/drm_crtc.h | 49 ++++++++++++++++++++++++++++++++++++ 7 files changed, 157 insertions(+), 1 deletion(-)