[PATCH v2 1/4] dt-bindings: simplefb: Specify node location and handoff related properties

On Thu, Nov 13, 2014 at 12:14 PM, Hans de Goede [off-list ref] wrote:

Hi,

On 11/13/2014 12:02 PM, Grant Likely wrote:

quoted

On Thu, Nov 13, 2014 at 8:50 AM, Hans de Goede [off-list ref] wrote:

quoted

Since simplefb nodes do not relate directly to hw typically they have been
placed in the root of the devicetree. As the represent runtime information
having them as sub-nodes of /chosen is more logical, specify this.

Also specify when to set the chosen stdout-path property to a simplefb node.

For reliable handover to a hardware specific driver, that driver needs to
know which simplefb to unregister when taking over, specify how the hw driver
can find the matching simplefb node.

Last add some advice on how to fill and use simplefb nodes from a firmware
pov.

Signed-off-by: Hans de Goede <redacted>
Acked-by: Geert Uytterhoeven <geert@linux-m68k.org>
--
Changes in v2:
-Add stdout-path to the example code
---
 .../bindings/video/simple-framebuffer.txt          | 38 +++++++++++++++++++++-
 1 file changed, 37 insertions(+), 1 deletion(-)

diff --git a/Documentation/devicetree/bindings/video/simple-framebuffer.txt b/Documentation/devicetree/bindings/video/simple-framebuffer.txt
index 8f35718..8b7ecf6 100644
--- a/Documentation/devicetree/bindings/video/simple-framebuffer.txt
+++ b/Documentation/devicetree/bindings/video/simple-framebuffer.txt

@@ -4,6 +4,26 @@ A simple frame-buffer describes a frame-buffer setup by firmware or
 the bootloader, with the assumption that the display hardware has already
 been set up to scan out from the memory pointed to by the reg property.

+Since simplefb nodes represent runtime information they must be sub-nodes of
+the chosen node (*). The primary display node must be named framebuffer0,
+additional nodes must be called framebuffer1, etc.

Thinking more about our conversation yesterday, the preferred name
should still be framebuffer@<address>. There is no reason to break
with established convention, and as mentioned in my reply on patch #2,
using the name is not the preferred way to identify a device node. So,
my recommendation is to prefer the name "framebuffer@<addr>", but if
it is inconvenient because the address isn't known, then
"framebuffer#" is acceptable.

Since we want to use pre-filled simplefb nodes already present in the devicetree,
and u-boot is the one chosing the framebuffer address we don't know the
address to put in the dts file beforehand, so framebuffer# it is.

fdt_set_name() is available to U-Boot to rename a node. :-)

Prepopulating with /chosen/framebuffer#, and then renaming to
/chosen/framebuffer@<addr> is perfectly reasonable.

g.