Re: [RFR 2/2] drm/panel: Add simple panel support

Stephen Warren
2013-10-24T22:06:18Z

On 10/24/2013 12:20 PM, Laurent Pinchart wrote:
> Hi Stephen,
>
> On Sunday 20 October 2013 23:07:36 Stephen Warren wrote:
>> On 10/17/2013 12:07 PM, Laurent Pinchart wrote:
>> ...
>>
>>>> As I said, anything that really needs a CDF binding to work
>>>> likely isn't "simple" anymore, therefore a separate driver can
>>>> easily be justified.
>>>
>>> The system as a whole would be more complex, but the panel could be
>>> the same. We can't have two drivers for the same piece of hardware
>>> in the DT world, as there will be a single compatible string and no
>>> way to choose between the drivers (unlike the board code world that
>>> could set device names to "foo- encoder-v4l2" or "foo-encoder-drm"
>>> and live happily with that ever after).
>>
>> That's not true. We can certainly define two different compatible
>> values for a piece of HW if we have to. We can easily control whether
>> they are handled by the same or different drivers in the OS.
>
> From an implementation point of view, sure. But from a conceptual point of
> view, that would make the DT bindings pretty Linux-specific, with a
> description of what the operating system should do instead of a description of
> what the hardware looks like. My understanding is that we've tried pretty hard
> in the past not to open that Pandora's box.
>
> The case I'm mostly concerned about would be two different compatibility
> strings to select whether the device should be handled by a KMS or V4L driver.
> I don't think that's a good idea.

I wouldn't think of the two compatible values as selecting different
specific Linux drivers, but rather they simply describe the HW in
different levels of detail. The fact that if we know a certain level of
detail about the HW means that Linux can and does create a KMS driver
rather than a V4L2 driver seems like a detail that's completely hidden
inside the OS.

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