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

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  Re: [PATCH v9 6/8] drivers:input:ads7846(+tsc2046): fix spi module table "H. Nikolaus Schaller" <hns@goldelico.com> - 2017-02-01 21:30 +0100
    Re: [PATCH v9 6/8] drivers:input:ads7846(+tsc2046): fix spi module  table Javier Martinez Canillas <javier@osg.samsung.com> - 2017-02-01 22:20 +0100
      Re: [PATCH v9 6/8] drivers:input:ads7846(+tsc2046): fix spi module  table Dmitry Torokhov <dmitry.torokhov@gmail.com> - 2017-02-01 23:30 +0100
        Re: [PATCH v9 6/8] drivers:input:ads7846(+tsc2046): fix spi module  table Javier Martinez Canillas <javier@osg.samsung.com> - 2017-02-02 00:00 +0100
        Re: [PATCH v9 6/8] drivers:input:ads7846(+tsc2046): fix spi module table "H. Nikolaus Schaller" <hns@goldelico.com> - 2017-02-02 06:50 +0100

#1571963 — Re: [PATCH v9 6/8] drivers:input:ads7846(+tsc2046): fix spi module table

Hi Dmitry, Javier,

> Am 29.01.2017 um 19:25 schrieb H. Nikolaus Schaller <hns@goldelico.com>:
> 
> Hi Dmitry,
> 
>> Am 29.01.2017 um 19:01 schrieb Dmitry Torokhov <dmitry.torokhov@gmail.com>:
>> 
>> 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@gmail.com>:
>>>> 
>>>> 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?

If not, I'd recommend to stay with the current level of optimality.

BR and thanks,
Nikolaus

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#1571989 — Re: [PATCH v9 6/8] drivers:input:ads7846(+tsc2046): fix spi module table

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@goldelico.com>:
>>
>> Hi Dmitry,
>>
>>> Am 29.01.2017 um 19:01 schrieb Dmitry Torokhov <dmitry.torokhov@gmail.com>:
>>>
>>> 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@gmail.com>:
>>>>>
>>>>> 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

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#1572023 — Re: [PATCH v9 6/8] drivers:input:ads7846(+tsc2046): fix spi module table

On Wed, Feb 01, 2017 at 06:14:39PM -0300, Javier Martinez Canillas wrote:
> 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@goldelico.com>:
> >>
> >> Hi Dmitry,
> >>
> >>> Am 29.01.2017 um 19:01 schrieb Dmitry Torokhov <dmitry.torokhov@gmail.com>:
> >>>
> >>> 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@gmail.com>:
> >>>>>
> >>>>> 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.

If the concern with drivers having I2C or SPI device table, but not OF
device table, then I think cocinnelle could be used to scan and find
them.

> 
> 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.

You can always build the module into kernel or load it by hand if it is
that important. Module autoloading does not work anyway if you have
several compatible strings, like

	compatible = "vendor,new-device", "vendor,generic-device";

Thanks.

-- 
Dmitry

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#1572038 — Re: [PATCH v9 6/8] drivers:input:ads7846(+tsc2046): fix spi module table

Hello Dmitry,

On 02/01/2017 07:28 PM, Dmitry Torokhov wrote:

[snip]

>>
>> 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.
> 
> If the concern with drivers having I2C or SPI device table, but not OF
> device table, then I think cocinnelle could be used to scan and find
> them.
>

I don't think coccinelle is a good fit for this since you may have to look if
a DTS is using in its compatible string a device that's in an SPI table or if
a DT binding documents this device as a compatible string.

But yes I get your point and I agree that is just a matter of having a script
to look for these. Someone should have the time to write it though :)

>>
>> 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.
> 
> You can always build the module into kernel or load it by hand if it is
> that important. Module autoloading does not work anyway if you have
> several compatible strings, like
> 
> 	compatible = "vendor,new-device", "vendor,generic-device";
> 
> Thanks.
>

Agree.

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

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#1572151

Hi,

> Am 01.02.2017 um 23:28 schrieb Dmitry Torokhov <dmitry.torokhov@gmail.com>:
> 
> On Wed, Feb 01, 2017 at 06:14:39PM -0300, Javier Martinez Canillas wrote:
>> 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@goldelico.com>:
>>>> 
>>>> Hi Dmitry,
>>>> 
>>>>> Am 29.01.2017 um 19:01 schrieb Dmitry Torokhov <dmitry.torokhov@gmail.com>:
>>>>> 
>>>>> 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@gmail.com>:
>>>>>>> 
>>>>>>> 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.
> 
> If the concern with drivers having I2C or SPI device table, but not OF
> device table, then I think cocinnelle could be used to scan and find
> them.
> 
>> 
>> 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.
> 
> You can always build the module into kernel or load it by hand if it is
> that important.

Well, it is the only exception on the OpenPandora that does NOT yet load
automatically from the DT.

And sure we can always find a hack or workaround in user-space for everything
the kernel isn't doing well.

> Module autoloading does not work anyway if you have
> several compatible strings, like
> 
> 	compatible = "vendor,new-device", "vendor,generic-device";

We don't use that mechanism here since there is only one ads7846 installed
and it won't change.

BR,
Nikolaus

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