Re: [PATCH v13 12/18] platform: Add __free() based cleanup function for platform_device_put

Greg KH
2024-10-14T16:12:36Z

On Mon, Oct 14, 2024 at 06:00:51PM +0200, Greg KH wrote:
> On Mon, Oct 14, 2024 at 04:43:39PM +0100, Jonathan Cameron wrote:
> > On Wed, 9 Oct 2024 13:41:13 +0100
> > <shiju.jose@huawei.com> wrote:
> >
> > > From: Jonathan Cameron <Jonathan.Cameron@huawei.com>
> > >
> > > Add __free() based cleanup function for platform_device_put().
> > >
> > > Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
> > > Signed-off-by: Shiju Jose <shiju.jose@huawei.com>
> > > ---
> > > include/linux/platform_device.h | 1 +
> > > 1 file changed, 1 insertion(+)
> > >
> > > diff --git a/include/linux/platform_device.h b/include/linux/platform_device.h
> > > index d422db6eec63..606533b88f44 100644
> > > --- a/include/linux/platform_device.h
> > > +++ b/include/linux/platform_device.h
> > > @@ -232,6 +232,7 @@ extern int platform_device_add_data(struct platform_device *pdev,
> > > extern int platform_device_add(struct platform_device *pdev);
> > > extern void platform_device_del(struct platform_device *pdev);
> > > extern void platform_device_put(struct platform_device *pdev);
> > > +DEFINE_FREE(platform_device_put, struct platform_device *, if (_T) platform_device_put(_T))
> > >
> > > struct platform_driver {
> > > int (*probe)(struct platform_device *);
> >
> > +CC Greg KH and Rafael.
> >
> > Makes sure to include them on v14 as this needs review from a driver core point
> > of view I think.
>
> Why is this needed for a platform device? This feels like you will have
> to do more work to "keep" the reference on the normal path than you to
> today to release the reference on the error path, right? Have a pointer
> to a patch that uses this?

Ah, is it this one:
https://lore.kernel.org/all/20241014164955.00003439@Huawei.com/
?

If so, no, that's an abuse of a platform device, don't do that, make a
REAL device on the bus that this device lives on. If it doesn't live on
a real bus, then put it on the virtual bus but do NOT abuse the platform
device layer for something like this.

thanks,

greg k-h