Re: [PATCH v9 6/8] drivers:input:ads7846(+tsc2046): fix spi module table

[Javier Martinez Canillas]

Hello Nikolaus,

On 02/01/2017 05:20 PM, H. Nikolaus Schaller wrote:
> Hi Dmitry, Javier,
> 
>> Am 29.01.2017 um 19:25 schrieb H. Nikolaus Schaller <hns@xxxxxxxxxxxxx>:
>>
>> Hi Dmitry,
>>
>>> Am 29.01.2017 um 19:01 schrieb Dmitry Torokhov <dmitry.torokhov@xxxxxxxxx>:
>>>
>>> On Sun, Jan 29, 2017 at 09:39:39AM +0100, H. Nikolaus Schaller wrote:
>>>> Hi Dmitry,
>>>>
>>>>> Am 28.01.2017 um 20:35 schrieb Dmitry Torokhov <dmitry.torokhov@xxxxxxxxx>:
>>>>>
>>>>> On Wed, Dec 28, 2016 at 03:53:21PM +0100, H. Nikolaus Schaller wrote:
>>>>>> Fix module table so that the driver is loaded if compiled
>>>>>> as module and requested by DT.
>>>>>>
>>>>>
>>>>> I believe I already replied to a similar patch: we alreadyhave necessary
>>>>> aliases in this driver, we need to fix module loading to use it.
>>>>
>>>> Yes, you did comment on [PATCH v6 7/8] (19 Nov 2016):
>>>>
>>>>>> We really need to fix it between spi/i23c core and module utils instead
>>>>>> of keeping adding duplicate IDs all over drivers. We already have OF
>>>>>> module device table containing the same data, we should be able to use
>>>>>> it.
>>>>
>>>> And Javier Martinez Canillas replied (23 Nov 2016):
>>>>
>>>>> Agreed, unfortunately until the I2C and SPI core are changed to properly
>>>>> report OF modaliases, we will have to keep adding these duplicated IDs.
>>>>>
>>>>> And changing the I2C and SPI core isn't trivial since it could break a
>>>>> lot of drivers that rely on a platform modalias being reported (i.e: no
>>>>> OF device IDs present in the drivers even when are registered via DT).
>>>>
>>>> Therefore I didn't see a need to change it.
>>>
>>> I agree that changing I2C and SPI core is not trivial, however this is
>>> no reason for piling up workarounds in all drivers. Are you seriously
>>> advocating going though *every* driver and copying OF data into I2C/SPI
>>> instead of doing the right thing and fixing the root of the issue?
>>
>> If you prefer to have this done (and I agree it would be a tiny improvement),
>> please do it for us all. But please after merging this workaround.
> 
> Have we been lucky to find someone who is able and willing to work on this?
>

As said, changing the core is trivial. A RFC patch is [0].

The problem is how to make sure that this change won't cause regressions
in existing drivers.

There was particularly tricky for the spi-nor driver, it doesn't help that
a lot of DT are using undocumented compatible strings (sometimes with no
vendor prefix). You can see the discussion here [1].

In the same thread Mark Brown said that it wasn't that bad to have the
information in the OF device ID table duplicated in a SPI device table.

Certainly isn't the best approach but IMHO is better than the module not
loading.

https://patchwork.kernel.org/patch/7041141/
https://patchwork.ozlabs.org/patch/545125/
 
> If not, I'd recommend to stay with the current level of optimality.
> 
> BR and thanks,
> Nikolaus
> 

Best regards,
-- 
Javier Martinez Canillas
Open Source Group
Samsung Research America