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

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Message-ID: <DM5PR12MB185098D36F665AC5702D47DDC05A9@DM5PR12MB1850.namprd12.prod.outlook.com>
Date:   Thu, 20 Jan 2022 10:29:10 +0000
From:   Akhil R <akhilrajeev@...dia.com>
To:     Andy Shevchenko <andy.shevchenko@...il.com>
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_*()

> ...
> 
> > > 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.

Thanks,
Akhil