[yocto] [meta-raspberrypi][PATCH v2 3/4] rpi-default-providers: Document how to switch providers for vc4 gfx stack

[Javier Martinez Canillas]

From: Derek Foreman <derekf at osg.samsung.com>

The Raspberry Pi boards can use one of two graphics stacks: The "userland"
user-space driver or the VC4 drm/kms kernel driver. This patch documents
how the user user can choose if the VC4 driver has to be used instead and
set the right preferred providers for that case.

Signed-off-by: Derek Foreman <derekf at osg.samsung.com>
[javier: Extend commit msg and made conditional instead removing userland]
Signed-off-by: Javier Martinez Canillas <javier at osg.samsung.com>

---

Changes in v2:
- Don't add a feature and allow users to change the default provider manually
  aided by a comment. Suggested by Andreas Müller and Andrei Gherzan.

 conf/machine/include/rpi-default-providers.inc | 10 ++++++++++
 1 file changed, 10 insertions(+)

diff --git a/conf/machine/include/rpi-default-providers.inc b/conf/machine/include/rpi-default-providers.inc
index ee3a3acce7bd..e007bbb60216 100644
--- a/conf/machine/include/rpi-default-providers.inc
+++ b/conf/machine/include/rpi-default-providers.inc
@@ -8,3 +8,13 @@ PREFERRED_PROVIDER_virtual/libgles2 ?= "userland"
 PREFERRED_PROVIDER_virtual/libgl ?= "mesa-gl"
 PREFERRED_PROVIDER_virtual/mesa ?= "mesa-gl"
 PREFERRED_PROVIDER_jpeg = "jpeg"
+
+# To use a kernel with the VC4 DRM/KMS driver instead, comment the
+# virtual kernel, egl, libgles2, libgl and mesa preferred provider
+# above and uncomment the following lines.
+#
+# PREFERRED_PROVIDER_virtual/kernel = "linux-raspberrypi-vc4"
+# PREFERRED_PROVIDER_virtual/egl ?= "mesa"
+# PREFERRED_PROVIDER_virtual/libgles2 ?= "mesa"
+# PREFERRED_PROVIDER_virtual/libgl ?= "mesa"
+# PREFERRED_PROVIDER_virtual/mesa ?= "mesa"
-- 
2.4.3