Re: [PATCH v2 1/4] omapdrm: fix compatible string for td028ttec1

[H. Nikolaus Schaller]

> Am 16.11.2017 um 18:08 schrieb Andrew F. Davis <afd@xxxxxx>:
> 
> On 11/16/2017 10:10 AM, H. Nikolaus Schaller wrote:
>> Hi Andrew,
>> 
>>> Am 16.11.2017 um 16:53 schrieb Andrew F. Davis <afd@xxxxxx>:
>>> 
>>> On 11/16/2017 07:43 AM, H. Nikolaus Schaller wrote:
>>>> 
>>>>> Am 16.11.2017 um 13:32 schrieb Tomi Valkeinen <tomi.valkeinen@xxxxxx>:
>>>>> 
>>>>> On 16/11/17 10:50, H. Nikolaus Schaller wrote:
>>>>>> The vendor name was "toppoly" but other panels and the vendor list
>>>>>> have defined it as "tpo". So let's fix it in driver and bindings.
>>>>>> 
>>>>>> Signed-off-by: H. Nikolaus Schaller <hns@xxxxxxxxxxxxx>
>>>>>> ---
>>>>> 
>>>>> 
>>>>>> -MODULE_ALIAS("spi:toppoly,td028ttec1");
>>>>>> +MODULE_ALIAS("spi:tpo,td028ttec1");
>>>>> 
>>>>> Doesn't this mean that the module won't load if you have old bindings?
>>>> 
>>>> Hm.
>>>> 
>>>> Well, I think it can load but doesn't automatically from DT strings which might
>>>> be unexpected.
>>>> 
>>>>> Can't we have two module aliases?
>>>> 
>>>> I think we can. Just a random example:
>>>> https://elixir.free-electrons.com/linux/latest/source/drivers/w1/slaves/w1_therm.c#L754
>>>> 
>>>> So we should keep both.
>>> 
>>> Even better would be to drop both MODULE_ALIAS and let the
>>> MODULE_DEVICE_TABLE macro define them for your from the SPI id table.
>> 
>> Why would that be better?
>> 
> 
> MODULE_ALIAS is ugly, you already have a table (usually) of device names
> that are supported by the driver, the module aliases should be generated
> from that table. This also keeps supported device list in one place.
> 
>> As far as I see it will need more code and changes than adding one line of
>> MODULE_ALIAS.
>> 
>>> Although it doesn't look like this driver has an SPI id table, you
>>> should probably add one, I be interested to see if this module is always
>>> being matched through the "spi" or the "of" alias..
>> 
>> Could you please propose how that code should look like, so that I can test?
>> 
> 
> Sure,
> 
> start with
> $ udevadm monitor
> and see what string the kernel is looking for when trying to find a
> module for this device.

Well, the module is loaded automatically from DT at boot time well before
I can start udevadm. So that is the most tricky part to setup the system
to suppress this...

> 
> If it is only ever looking for "of:toppoly,td028ttec1", then you can
> drop the MODULE_ALIAS and be done as it was never getting used anyway.

Since it is an SPI client, I am sure it looks for "spi:something.

> 
> What I expect though is "spi:toppoly,td028ttec1", in which case you
> should add
> 
> static const struct spi_device_id td028ttec1_ids[] = {
> 	{ "toppoly,td028ttec1", 0 },
> 	{ "tpo,td028ttec1", 0},
> 	{ /* sentinel */ }
> };
> MODULE_DEVICE_TABLE(spi, td028ttec1_ids);

We already have a static const struct of_device_id td028ttec1_of_match[]
table with the same information.

So we still have two places to keep in sync.

Or can we remove the td028ttec1_of_match[]? AFAIK not.

> 
> link to it in the td028ttec1_spi_driver struct:
> .id_table = td028ttec1_ids,
> 
> Then test again to see that the module still loads with the new and old
> DT string.

In total I am not really convinced that adding 7 lines of code is better
than one (the "tpo," alias) that is tested and works...

And it looks like a lot of unplanned code testing for me which takes more
than 5 minutes :)

So I'd prefer to leave that exercise of fixing the MODULE_ALIAS/DEVICE_TABLE
to someone else...

BR and thanks,
Nikolaus

> 
> Andrew
> 
>> BR and thanks,
>> Nikolaus Schaller
>> 
>>> 
>>>> 
>>>> Should I submit a new version?
>>>> 
>>>> BR,
>>>> Nikolaus
>>>> 
>>>> --
>>>> To unsubscribe from this list: send the line "unsubscribe devicetree" in
>>>> the body of a message to majordomo@xxxxxxxxxxxxxxx
>>>> More majordomo info at  http://vger.kernel.org/majordomo-info.html
>>>> 
>> 
>> --
>> To unsubscribe from this list: send the line "unsubscribe devicetree" in
>> the body of a message to majordomo@xxxxxxxxxxxxxxx
>> More majordomo info at  http://vger.kernel.org/majordomo-info.html
>>