linux-kernel - Re: [PATCH] usb-hid-core: Set intfdata to NULL if probe fails

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Message-ID: <alpine.LNX.2.00.1205230012010.30445@pobox.suse.cz>
Date:	Wed, 23 May 2012 00:14:15 +0200 (CEST)
From:	Jiri Kosina <jkosina@...e.cz>
To:	Greg KH <gregkh@...uxfoundation.org>
Cc:	Hans de Goede <hdegoede@...hat.com>, Jiri Slaby <jslaby@...e.cz>,
	linux-kernel@...r.kernel.org, USB list <linux-usb@...r.kernel.org>
Subject: Re: [PATCH] usb-hid-core: Set intfdata to NULL if probe fails

On Tue, 22 May 2012, Greg KH wrote:

> > > Well then lets work towards making it guaranteed, since I still believe
> > > the following holds true:
> > > 1) drvdata is for a driver to store a pointer to driver specific data
> > > 2) If no driver is bound, there is no driver specific data associated with
> > >    the device
> > > 3) Thus logically drvdata should be NULL if no driver is bound.
> > > 
> > > I'll do a patch for the USB-core to ensure that intfdata gets set to NULL
> > > on probe failure.
> > 
> > Hans,
> > 
> > I believe this is a good thing per se, but shouldn't this rather be done 
> > in driver core, to guarantee that this hold across all buses?
> 
> Maybe, but that would require that the driver core set the field to NULL
> after every probe call that fails?  Is that really necessary to fix up
> bugs in different bus subsystems that forget to clean up properly?
> 
> I'm not saying it's a bad thing to change it there, it just seems a bit
> heavy-handed for a very rare event.

The question is where does the requirement get imposed on the individual 
buses to actually reset drvdata? I don't think this has been 
'standardized', so resetting it in a driver core seems natural.

All in all, it has to be done anyway, so it makes sense to me to be done 
in as common code place as possible.

Thanks,

-- 
Jiri Kosina
SUSE Labs
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