Re: [PATCH 2/3] drm/bridge: Add ti-ftp410 HDMI transmitter driver

[Tomi Valkeinen <tomi.valkeinen@ti.com>]

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On 14/11/16 13:10, Laurent Pinchart wrote:
> Hi Jyri,
> 
> On Monday 14 Nov 2016 10:49:43 Jyri Sarha wrote:
>> On 11/03/16 19:46, Laurent Pinchart wrote:
>>>> +Required properties:
>>>>> +	- compatible: "ti,tfp410"
>>>
>>> The device is an I2C slave, it should have a reg property. Given that the
>>> chip can be used without being controlled through I2C, the reg property
>>> should be optional. You should document this clearly, and explain how the
>>> DT node can be instantiated as a child of an I2C controller when the I2C
>>> interface is used, or in other parts of the device tree otherwise.
>>
>> Shouldn't I have two different compatible strings if want to make both
>> platform driver probe and i2c client probe to work?
> 
> I don't think so, it's still the same chip.
> 
>> Or can it be done with single compatible string? Would you know of an
>> example of such a driver?
> 
> You will need to register both a i2c_driver and a platform_driver in the 
> tfp410 driver. Both will advertise the same compatible string. As you'll have 
> two probe functions, it should be easy to handle the differences between the 

If you have the same compatible string, won't both probes trigger? If
so, how does, e.g., the platform driver know this is actually i2c case,
and bail out? And if both probes don't trigger, why not? How does the
device probing machinery know that this DT node is actually an i2c node,
not a platform device node?

 Tomi


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