From 447a9e8921cd21c8eded433fbb36929e4544cca1 Mon Sep 17 00:00:00 2001 From: Simon Ser Date: Fri, 13 Aug 2021 12:38:05 +0200 Subject: [PATCH] Document why the primary plane is a special case For instance, i915 requires the primary plane to be enabled. --- alloc.c | 6 ++++-- 1 file changed, 4 insertions(+), 2 deletions(-) diff --git a/alloc.c b/alloc.c index 912dd67..06ce1dc 100644 --- a/alloc.c +++ b/alloc.c @@ -52,8 +52,10 @@ * * In practice, the primary plane is treated separately. This is where layers * that can't be mapped to any plane (e.g. layer 1 in our example) will be - * composited. The primary plane is the first that will be allocated. Then all - * other planes will be allocated, from the topmost one to the bottommost one. + * composited. The primary plane is the first that will be allocated, because + * some drivers require it to be enabled in order to light up any other plane. + * Then all other planes will be allocated, from the topmost one to the + * bottommost one. * * The "zpos" property (which defines ordering between layers/planes) is handled * as a special case. If it's set on layers, it adds additional constraints on