linux-kernel - Re: patch driver-core-warn-about-duplicate-driver-names-on-the-same-bus.patch added to gregkh-2.6 tree

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Message-ID: <s5hr6cowr4f.wl%tiwai@suse.de>
Date:	Tue, 29 Apr 2008 18:41:20 +0200
From:	Takashi Iwai <tiwai@...e.de>
To:	Greg KH <gregkh@...e.de>
Cc:	Stas Sergeev <stsp@...et.ru>,
	Linux kernel <linux-kernel@...r.kernel.org>,
	Dmitry Torokhov <dmitry.torokhov@...il.com>
Subject: Re: patch	driver-core-warn-about-duplicate-driver-names-on-the-same-bus.patch	added to gregkh-2.6 tree

At Tue, 29 Apr 2008 08:14:36 -0700,
Greg KH wrote:
> 
> On Tue, Apr 29, 2008 at 12:41:56PM +0200, Takashi Iwai wrote:
> > At Mon, 28 Apr 2008 21:58:49 -0700,
> > Greg KH wrote:
> > > 
> > > On Tue, Apr 29, 2008 at 08:48:08AM +0400, Stas Sergeev wrote:
> > > > Hello.
> > > > 
> > > > gregkh@...e.de wrote:
> > > > > This is a note to let you know that I've just added the patch titled
> > > > >      Subject: driver core: warn about duplicate driver names on the same bus
> > > > > to my gregkh-2.6 tree.  Its filename is
> > > > Thanks.
> > > > 
> > > > Takashi, do you think this fixes the
> > > > pcspkr/snd-pcsp conflict sufficienly
> > > > well? I think the Kconfig protection
> > > > is no longer needed. For the better
> > > > convinience the modprobe rule can be
> > > > created that will remove one driver
> > > > before inserting another. But this is
> > > > optional.
> > > 
> > > No, don't rely on the driver core warning and catching code errors like
> > > this, that's not a good idea at all.  I like the warning and your patch,
> > > but don't assume it's always going to be there.
> > 
> > But multiple drivers for the same device are allowed on other buses
> > like PCI.  I think this is no reason to prohibit the multiple platform
> > drivers for the same platform device.
> 
> No, the driver core doesn't allow that at all right now (I'm working on
> fixing that though...)
> 
> What this patch did is just not allow you to have the same "name" for
> the driver on the same bus, which is reasonable as without the check,
> sysfs complains about trying to create a duplicate name in the same
> directory.
> 
> Different names is fine, and I'll continue to work on the ability to
> allow multiple drivers for the same device at the same time...

Well, I wasn't clear enough -- currently we prohibit the *build* of
snd-pcsp driver when input pcspkr driver is built, regardless whether
module or built-in.  The reason is that sysfs spews an error with a
stack trace when the platform name conflicts, and this appears to be a
serious error.  Disabling the build is the simplest solution in such a
case (when considering built-in driver).

Now, with this patch, the platform name conflict appears non-critical,
and the driver should handle properly for the returned error code.
Thus, there shouldn't be a big obstacle to *build* both drivers.


Takashi
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