linux-kernel - Re: [PATCH v13 12/18] platform: Add __free() based cleanup function for platform_device

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Message-ID: <2024101451-reword-animation-2179@gregkh>
Date: Mon, 14 Oct 2024 18:04:37 +0200
From: Greg KH <gregkh@...uxfoundation.org>
To: Jonathan Cameron <Jonathan.Cameron@...wei.com>
Cc: shiju.jose@...wei.com, linux-edac@...r.kernel.org,
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	linuxarm@...wei.com
Subject: Re: [PATCH v13 12/18] platform: Add __free() based cleanup function
 for platform_device_put

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@...wei.com> wrote:
> > 
> > > From: Jonathan Cameron <Jonathan.Cameron@...wei.com>
> > > 
> > > Add __free() based cleanup function for platform_device_put().
> > > 
> > > Signed-off-by: Jonathan Cameron <Jonathan.Cameron@...wei.com>
> > > Signed-off-by: Shiju Jose <shiju.jose@...wei.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