linux-kernel - Re: [PATCH v1 1/3] hwmon: (pwm-fan) Make use of device properties

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Message-ID: <CAHp75Vf+-4U6OW4sf+mKsPt8WoRL_jN-sYtzOMzhhH8--+OU1w@mail.gmail.com>
Date:   Fri, 19 Aug 2022 12:56:42 +0300
From:   Andy Shevchenko <andy.shevchenko@...il.com>
To:     Guenter Roeck <linux@...ck-us.net>
Cc:     Andy Shevchenko <andriy.shevchenko@...ux.intel.com>,
        Uwe Kleine-König 
        <u.kleine-koenig@...gutronix.de>,
        Linux Documentation List <linux-doc@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        linux-pwm@...r.kernel.org, linux-hwmon@...r.kernel.org,
        Jonathan Corbet <corbet@....net>,
        Thierry Reding <thierry.reding@...il.com>,
        Jean Delvare <jdelvare@...e.com>,
        Bartlomiej Zolnierkiewicz <b.zolnierkie@...sung.com>
Subject: Re: [PATCH v1 1/3] hwmon: (pwm-fan) Make use of device properties

On Fri, Aug 19, 2022 at 2:41 AM Guenter Roeck <linux@...ck-us.net> wrote:
> On Sat, Aug 06, 2022 at 06:25:15PM +0300, Andy Shevchenko wrote:
> > Convert the module to be property provider agnostic and allow
> > it to be used on non-OF platforms.
> >
> > Add mod_devicetable.h include.
> >
> > Signed-off-by: Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
> > Acked-by: Uwe Kleine-König <u.kleine-koenig@...gutronix.de>
>
> I had another look at this patch. A substantial part of the changes
> is because device properties don't support of_property_read_u32_index(),
> reworking the code to use device_property_read_u32_array() instead.
> Sorry, I don't like it, it results in a substantial number of unnecessary
> changes. Device properties should support the equivalent of
> of_property_read_u32_index() instead to simplify conversions.

Not all (device property) providers can have such API available. Are
you suggesting to
 a) alloc memory for entire array;
 b) cache one for a given index;
 c) free a memory;
 d) loop as many times as index op is called.

Sorry, this is way too far and non-optimal in comparison to the
substantial number of unnecessary changes (two or three small
refactorings?).

Another way is to provide a pwm-fan-acpi, which will be the copy of
the driver after this patch is applied. I don't think it's a very
bright idea either.

-- 
With Best Regards,
Andy Shevchenko