linux-kernel - Re: [PATCH v2 3/3] i2c: smbus: Use device_*() functions instead of of

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Date:   Thu, 20 Jan 2022 12:43:02 +0200
From:   Andy Shevchenko <andy.shevchenko@...il.com>
To:     Akhil R <akhilrajeev@...dia.com>,
        Uwe Kleine-König 
        <u.kleine-koenig@...gutronix.de>
Cc:     Christian Koenig <christian.koenig@....com>,
        Dmitry Osipenko <digetx@...il.com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Jonathan Hunter <jonathanh@...dia.com>,
        Laxman Dewangan <ldewangan@...dia.com>,
        linux-i2c <linux-i2c@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        linux-tegra <linux-tegra@...r.kernel.org>,
        "Rafael J. Wysocki" <rafael@...nel.org>,
        Sumit Semwal <sumit.semwal@...aro.org>,
        Thierry Reding <thierry.reding@...il.com>,
        Wolfram Sang <wsa@...nel.org>, Len Brown <lenb@...nel.org>,
        ACPI Devel Maling List <linux-acpi@...r.kernel.org>
Subject: Re: [PATCH v2 3/3] i2c: smbus: Use device_*() functions instead of of_*()

On Thu, Jan 20, 2022 at 12:29 PM Akhil R <akhilrajeev@...dia.com> wrote:
>
> > ...
> >
> > > > This change reveals potential issue:
> > > >
> > > > > -               irq = of_irq_get_byname(adapter->dev.of_node, "smbus_alert");
> > > > > +               irq = device_irq_get_byname(adapter->dev.parent,
> > "smbus_alert");
> > > >
> > > > >                 if (irq <= 0)
> > > >
> > > > I guess this '= 0' part should be fixed first.
> > >
> > > '0' is a failure as per the documentation of of_irq_get_byname() as well as
> > > of_irq_get(). The case is different for acpi_irq_get(), but it is handled in
> > > fwnode_irq_get(). If I understood it right, a return value of '0' should be
> > > considered a failure here.
> >
> > Depends. I have no idea what the original code does here. But
> > returning an error or 0 from this function seems confusing to me.
> >
> The description in of_irq_get*() says -
> /* Return: Linux IRQ number on success, or 0 on the IRQ mapping failure, or
>  * -EPROBE_DEFER if the IRQ domain is not yet created, or error code in case
>  * of any other failure.
>  */
> As I see from the code of fwnode_irq_get(), which is used in this case, returns
> either the return value of of_irq_get() or error code from acpi_irq_get() when
> it fails, or res.start if it didn't fail. I guess, any of these would not be 0 unless
> there is an error.

of_irq_get*() seems inconsistent...

Uwe, what do you think?

-- 
With Best Regards,
Andy Shevchenko