From: Pekka Paalanen Date: Mon, 14 Apr 2025 08:56:56 +0000 (+0000) Subject: drm/doc: document front-buffer rendering X-Git-Tag: v6.16-rc1~144^2~11^2~31 X-Git-Url: http://git.ipfire.org/?a=commitdiff_plain;h=9b33df36b45136d301241920d13a0a3ecc77b8f9;p=thirdparty%2Flinux.git drm/doc: document front-buffer rendering Explain how to perform front-buffer rendering. v2: apply Pekka's rewrite Signed-off-by: Pekka Paalanen Signed-off-by: Simon Ser Reviewed-by: Simon Ser Link: https://lore.kernel.org/r/20250414085652.43904-1-contact@emersion.fr --- diff --git a/drivers/gpu/drm/drm_blend.c b/drivers/gpu/drm/drm_blend.c index 6e74de8334663..6852d73c931ce 100644 --- a/drivers/gpu/drm/drm_blend.c +++ b/drivers/gpu/drm/drm_blend.c @@ -75,6 +75,12 @@ * the currently visible vertical area of the &drm_crtc. * FB_ID: * Mode object ID of the &drm_framebuffer this plane should scan out. + * + * When a KMS client is performing front-buffer rendering, it should set + * FB_ID to the same front-buffer FB on each atomic commit. This implies + * to the driver that it needs to re-read the same FB again. Otherwise + * drivers which do not employ continuously repeated scanout cycles might + * not update the screen. * CRTC_ID: * Mode object ID of the &drm_crtc this plane should be connected to. *