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

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Message-ID: <CAHp75VetU7_sJ-n6UHgFE+NU56t2Gw83x9E+OHETZkyxyF1qBQ@mail.gmail.com>
Date:   Sat, 20 Aug 2022 02:32:22 +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 4:09 PM Guenter Roeck <linux@...ck-us.net> wrote:
>
> On Fri, Aug 19, 2022 at 12:56:42PM +0300, Andy Shevchenko wrote:
> > 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.
> >
> An alternative might be to split the patch in two parts, one replacing
> of_property_read_u32_index() with of_property_read_u32_array() as
> preparation, with the above rationale and a note that this is to
> prepare for the switch to device properties, and then the actual device
> property switch. Some context showing how other conversions handled this
> problem would also be nice, though not necessary.

Thanks for the idea, I like it and it would indeed simplify the
understanding of the changes made.

-- 
With Best Regards,
Andy Shevchenko