linux-kernel - Re: [RESEND PATCH v5 5/5] input: joystick: Add ADC attached joystick driver.

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Message-Id: <0HGZ8Q.TO6FK92GVGIN3@crapouillou.net>
Date:   Sat, 18 Apr 2020 14:10:12 +0200
From:   Paul Cercueil <paul@...pouillou.net>
To:     Andy Shevchenko <andy.shevchenko@...il.com>
Cc:     Artur Rojek <contact@...ur-rojek.eu>,
        Dmitry Torokhov <dmitry.torokhov@...il.com>,
        Rob Herring <robh+dt@...nel.org>,
        Mark Rutland <mark.rutland@....com>,
        Jonathan Cameron <jic23@...nel.org>,
        Heiko Stuebner <heiko@...ech.de>,
        linux-input <linux-input@...r.kernel.org>,
        devicetree <devicetree@...r.kernel.org>,
        linux-iio <linux-iio@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [RESEND PATCH v5 5/5] input: joystick: Add ADC attached joystick
 driver.



Le sam. 18 avril 2020 à 14:57, Andy Shevchenko 
<andy.shevchenko@...il.com> a écrit :
> On Sat, Apr 18, 2020 at 1:48 AM Paul Cercueil <paul@...pouillou.net> 
> wrote:
>> 
>> 
>> 
>>  Le sam. 18 avril 2020 à 0:49, Andy Shevchenko
>>  <andy.shevchenko@...il.com> a écrit :
>>  > On Sat, Apr 18, 2020 at 12:24 AM Paul Cercueil 
>> <paul@...pouillou.net>
>>  > wrote:
>>  >>  Le sam. 18 avril 2020 à 0:10, Andy Shevchenko
>>  >>  <andy.shevchenko@...il.com> a écrit :
>>  >>  > On Fri, Apr 17, 2020 at 11:21 PM Artur Rojek
>>  >> <contact@...ur-rojek.eu>
>>  >>  > wrote:
>>  >
>>  > ...
>>  >
>>  >>  >>  +#include <linux/of.h>
>>  >>  >
>>  >>  > Do you really need this? (See below as well)
>>  >
>>  >>  >>  +static const struct of_device_id adc_joystick_of_match[] = 
>> {
>>  >>  >>  +       { .compatible = "adc-joystick", },
>>  >>  >>  +       { },
>>  >>  >>  +};
>>  >>  >>  +MODULE_DEVICE_TABLE(of, adc_joystick_of_match);
>>  >>  >>  +
>>  >>  >>  +static struct platform_driver adc_joystick_driver = {
>>  >>  >>  +       .driver = {
>>  >>  >>  +               .name = "adc-joystick",
>>  >>  >
>>  >>  >>  +               .of_match_table =
>>  >>  >> of_match_ptr(adc_joystick_of_match),
>>  >>  >
>>  >>  > Drop this a bit harmful of_match_ptr() macro. It should go 
>> with
>>  >> ugly
>>  >>  > #ifdeffery. Here you simple introduced a compiler warning.
>>  >>
>>  >>  I assume you mean #ifdef around the of_device_id + module table
>>  >> macro?
>>  >
>>  > Yes.
>>  >
>>  >>  > On top of that, you are using device property API, OF use in 
>> this
>>  >> case
>>  >>  > is contradictory (at lest to some extend).
>>  >>
>>  >>  I don't see why. The fact that the driver can work when probed 
>> from
>>  >>  platform code
>>  >
>>  > Ha-ha, tell me how. I would like to be very surprised.
>> 
>>  iio_map_array_register(),
>>  pinctrl_register_mappings(),
>>  platform_add_devices(),
>> 
>>  you're welcome.
> 
> I think above has no relation to what I'm talking about.

Yes it does. It allows you to map the IIO channels, set the pinctrl 
configurations and register a device from platform code instead of 
devicetree.

> How *this* driver can work as a platform instantiated one?
> We seems have a conceptual misunderstanding here.
> 
> For example, how can probe of this driver not fail, if it is not
> backed by a DT/ACPI properties?

platform_device_add_properties().

> 
>>  >>  doesn't mean that it shouldn't have a table to probe
>>  >>  from devicetree.
>>  >
>>  > I didn't get what you are talking about here. The idea of 
>> _unified_
>>  > device property API is to get rid of OF-centric code in favour of 
>> more
>>  > generic approach. Mixing those two can be done only in specific 
>> cases
>>  > (here is not the one).
>> 
>>  And how are we mixing those two here? The only OF-centric thing 
>> here is
>>  the device table, which is required if we want the driver to probe 
>> from
>>  devicetree.
> 
> Table is fine(JFYI the types and sections are defined outside of OF
> stuff, though being [heavily] used by it) , API (of_match_ptr() macro
> use) is not.

Sorry, but that's just stupid. Please have a look at how of_match_ptr() 
macro is defined in <linux/of.h>.

-Paul