Re: platform_data in i2c device drivers

[Frank Bormann <fbormann-/E1597aS9LQAvxtiuMwx3w@public.gmane.org>]

Hi Laurent,

Thank you again for explaining. One last question if that's okay.

If I have i2c_board_info being passed in to the probe function through the 
platform_data pointer and I also have the same, similar or maybe even 
conflicting configuration information in the DTB, is there any of the two that 
is supposed to take precedence or should that be an error case?

Thanks,
Frank

On 20/03/14 01:51 PM, Laurent Pinchart wrote:
> Hi Frank,
>
> On Thursday 20 March 2014 13:16:35 Frank Bormann wrote:
>> Hi Ben,
>>
>>> I think client->dev should be avoided if at-all possible. Many
>>> drivers keep their own local copy of platform data or the pointer
>>> to it in their driver private information.
>>
>> I was thinking about that. But then again, I'd either have to copy the
>> client->dev.platform_data pointer over to the private data, if it is
>> non-null, or I would have to use some variation of
>>
>> pdata = client->dev.platform_data ? client->dev.platform_data : priv_pd;
>>
>> every time I want to access the configuration. Guess, that's not so bad
>> though.
>
> Most drivers store a pointer to the platform data or a copy of the platform
> data in a per-device driver private structure. They populate that pointer or
> copy from the platform data pointer (in the legacy case) or from the device
> tree content. Outside of the probe function the driver thus only accesses its
> private pointer or copy.
>