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

[Hans de Goede <hdegoede@redhat.com>]

Hi,

On 11/13/2014 01:36 PM, Grant Likely wrote:
> On Thu, Nov 13, 2014 at 12:14 PM, Hans de Goede <hdegoede@redhat.com> wrote:
>> Hi,
>>
>> On 11/13/2014 12:02 PM, Grant Likely wrote:
>>> On Thu, Nov 13, 2014 at 8:50 AM, Hans de Goede <hdegoede@redhat.com> wrote:
>>>> 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 <hdegoede@redhat.com>
>>>> 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.

Ok, that works for me.

Regards,

Hans