linux-kernel - Re: [PATCH 2/5] gpio: davinci: Use dev name for label and automatic base selection

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Message-ID: <0e199aa3-2d9d-4e7d-af23-8523722f017a@ti.com>
Date:   Sat, 8 Sep 2018 14:41:22 -0500
From:   Grygorii Strashko <grygorii.strashko@...com>
To:     Keerthy <j-keerthy@...com>,
        Linus Walleij <linus.walleij@...aro.org>
CC:     "Andrew F. Davis" <afd@...com>, "Nori, Sekhar" <nsekhar@...com>,
        Kevin Hilman <khilman@...nel.org>,
        "open list:GPIO SUBSYSTEM" <linux-gpio@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 2/5] gpio: davinci: Use dev name for label and automatic
 base selection



On 09/06/2018 09:16 AM, Keerthy wrote:
> 
> 
> On Wednesday 05 September 2018 04:07 PM, Linus Walleij wrote:
>> On Mon, Sep 3, 2018 at 7:40 AM Keerthy <j-keerthy@...com> wrote:
>>> On Saturday 01 September 2018 12:43 AM, Andrew F. Davis wrote:
>>>> Use dev_name to get a unique label and use -1 for a base to get our
>>>> selection automatically. We pull in all GPIOs per chip now so this
>>>> does not have the effect of out of order labels like before.
>>>>
>>>> We do these both together so we can drop all the static data in one
>>>> patch. This also lets us normalize the return paths as we don't need
>>>> any cleanup after this change.
>>>
>>> echo 28 > /sys/class/gpio/export
>>> / # echo 28 > /sys/class/gpi[   12.839205] export_store: invalid GPIO 28
>>> o/export
>>> echo 2 > /sys/class/gp[   22.165728] export_store: invalid GPIO 2
>>> io/export
>>> / # echo 1 > /sys/class/gp[   25.961392] export_store: invalid GPIO 1
>>> io/export
>>> / # echo 3 > /sys/class/gp[   29.981918] export_store: invalid GPIO 3
>>> io/export
>>>
>>> Export fails with this patch. I am testing this on keystone-k2g-evm.
>>
>> I think the GPIO got a new number didn't it?
>>
>> Did you check the gpio file in debugfs to see which number
>> it got.
> 
> Okay now its numbered differently:
> 
> cat /sys/class/gpio/gpiochip340/ngpio
> 144
> 
> cat /sys/class/gpio/gpiochip272/ngpio
> 68

could you or Andrew provide content of /debug/gpio before/after?
And ls /sys/class/gpio/?
> 
> So gpio bank2 and bank1 have different gpio numbers. Is that acceptable?
> 
>>
>> This is sadly the global numberspace that we are tying to
>> get rid of (new apps/scripts should use the chardev).
>>
>> Are there applications that rely on the sysfs ABI on DaVinci?
>>
>> In that case base needs to be prerseved.

Not only base, but label also - /sys/class/gpio/gpiochip0/label, as this is
the way to find proper GPIO chip in sysfs using legacy GPIO ABI.

Linus, this platform is old and most of the users do not use new ABI (chardev),
so we could try change this, but need to be prepared for regressions reports.

-- 
regards,
-grygorii