linux-kernel - Re: [PATCH v4 1/1] device property: Allow error pointer to be passed to fwnode APIs

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Date:   Tue, 8 Mar 2022 20:03:28 +0100
From:   "Rafael J. Wysocki" <rafael@...nel.org>
To:     Heikki Krogerus <heikki.krogerus@...ux.intel.com>,
        Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
Cc:     ACPI Devel Maling List <linux-acpi@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Daniel Scally <djrscally@...il.com>,
        Sakari Ailus <sakari.ailus@...ux.intel.com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        "Rafael J. Wysocki" <rafael@...nel.org>,
        Len Brown <lenb@...nel.org>,
        Nuno Sá <nuno.sa@...log.com>
Subject: Re: [PATCH v4 1/1] device property: Allow error pointer to be passed
 to fwnode APIs

On Tue, Mar 8, 2022 at 3:36 PM Heikki Krogerus
<heikki.krogerus@...ux.intel.com> wrote:
>
> On Tue, Mar 08, 2022 at 02:37:12PM +0200, Andy Shevchenko wrote:
> > Some of the fwnode APIs might return an error pointer instead of NULL
> > or valid fwnode handle. The result of such API call may be considered
> > optional and hence the test for it is usually done in a form of
> >
> >       fwnode = fwnode_find_reference(...);
> >       if (IS_ERR(fwnode))
> >               ...error handling...
> >
> > Nevertheless the resulting fwnode may have bumped the reference count
> > and hence caller of the above API is obliged to call fwnode_handle_put().
> > Since fwnode may be not valid either as NULL or error pointer the check
> > has to be performed there. This approach uglifies the code and adds
> > a point of making a mistake, i.e. forgetting about error point case.
> >
> > To prevent this, allow an error pointer to be passed to the fwnode APIs.
> >
> > Fixes: 83b34afb6b79 ("device property: Introduce fwnode_find_reference()")
> > Reported-by: Nuno Sá <nuno.sa@...log.com>
> > Signed-off-by: Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
> > Tested-by: Nuno Sá <nuno.sa@...log.com>
> > Reviewed-by: Sakari Ailus <sakari.ailus@...ux.intel.com>
> > Acked-by: Nuno Sá <nuno.sa@...log.com>
>
> This is nice! FWIW:
>
> Reviewed-by: Heikki Krogerus <heikki.krogerus@...ux.intel.com>

Applied as 5.18 material, thanks!