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

Stephen Warren
2013-10-25T15:29:27Z

On 10/25/2013 12:33 PM, Laurent Pinchart wrote:
> On Thursday 24 October 2013 23:06:18 Stephen Warren wrote:
>> On 10/24/2013 12:20 PM, Laurent Pinchart wrote:
...
>>> 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.
>
> I expect the same level of details to be needed on both the KMS and V4L sides.
> Taking the example of the ADV7511 HDMI transmitter, the only change in the DT
> bindings between KMS and V4L would be the compatible string. "adi,adv7511-v4l"
> and "adi,adv7511-kms" is an option that I don't really like. Renaming -v4l and
> -kms to different names wouldn't fundamentally change the problem.

Yes, two compatible values such as "adi,adv7511-v4l" and
"adi,adv7511-kms" sounds like a bad idea.

Rather, shouldn't we have just "adi,adv7511", and the driver for that
should register itself in a way that allows either/both the top-level
DRM or top-level V4L drivers to find it, and make use of its services.
There are plenty of drivers in the kernel already that export services
through two different subsystems, e.g. a GPIO HW module that registers
as both a struct gpio_chip and a struct irq_chip, or both a struct
gpio_chip and a pinctrl device.
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