[PATCH] watchdog: ixp4xx: fix reference leak on platform_device_register() failure

[Guangshuo Li]

Hi Linus, Guenter,

Thanks for reviewing and discussing this.

On Mon, 20 Apr 2026 at 05:34, Linus Walleij <linusw at kernel.org> wrote:
>
> On Sun, Apr 19, 2026 at 11:08 PM Guenter Roeck <linux at roeck-us.net> wrote:
> > On 4/19/26 13:22, Linus Walleij wrote:
>
> > > Hi Guangshuo,
> > >
> > > thanks for your patch!
> > >
> > > On Mon, Apr 13, 2026 at 5:47 PM Guangshuo Li <lgs201920130244 at gmail.com> wrote:
> > >
> > >> ixp4xx_timer_probe() directly returns the result of
> > >> platform_device_register(&ixp4xx_watchdog_device). When registration
> > >> fails, the embedded struct device in ixp4xx_watchdog_device has already
> > >> been initialized by device_initialize(), but the failure path does not
> > >> drop the device reference, leading to a reference leak.
> > > (...)
> > >
> > >> -       return platform_device_register(&ixp4xx_watchdog_device);
> > >> +       ret = platform_device_register(&ixp4xx_watchdog_device);
> > >> +       if (ret)
> > >> +               platform_device_put(&ixp4xx_watchdog_device);
> > >
> > > If the problem in the description is indeed there, it seems the bug
> > > is inside platform_device_register(), surely a function returning an
> > > error code is supposed to clean up any resources it takes before
> > > returning an error. It seems wrong to try to fix this in all the
> > > consumers.
> > >
> >
> >  From platform_device_register():
> >
> > /**
> >   * platform_device_register - add a platform-level device
> >   * @pdev: platform device we're adding
> >   *
> >   * NOTE: _Never_ directly free @pdev after calling this function, even if it
> >   * returned an error! Always use platform_device_put() to give up the
> >   * reference initialised in this function instead.
> >   */
> >
> > Not that any code actually does that as far as I can see, but isn't
> > the above doing exactly what the comment suggests ?
>
> Yeah and Johan Hovold wrote that comment and he usually knows
> what he's doing so let's go with this then, I'm convinced!
>
> Reviewed-by: Linus Walleij <linusw at kernel.org>
>
> Yours,
> Linus Walleij

After further checking, this patch is not appropriate for this driver.
ixp4xx_watchdog_device is a static platform_device, and it does not have
a dev.release callback. Calling platform_device_put() on the
platform_device_register() failure path can therefore trigger the missing
release callback warning.

So please disregard this patch. I will drop it and will also go back and
check the other patches I sent for the same pattern, and send follow-ups
where they should be ignored or reverted.

Sorry for the confusion, and thanks again for the review.

Best regards,
Guangshuo Li