linux-kernel - Re: [PATCH v2 0/5] mfd: Fix platform device ids to avoid probe failure

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Message-ID: <20150325110231.GC10412@localhost>
Date:	Wed, 25 Mar 2015 12:02:31 +0100
From:	Johan Hovold <johan@...nel.org>
To:	Bartlomiej Zolnierkiewicz <b.zolnierkie@...sung.com>
Cc:	Johan Hovold <johan@...nel.org>, Lee Jones <lee.jones@...aro.org>,
	Samuel Ortiz <sameo@...ux.intel.com>,
	Support Opensource <support.opensource@...semi.com>,
	Milo Kim <milo.kim@...com>,
	patches@...nsource.wolfsonmicro.com,
	Fabio Estevam <fabio.estevam@...escale.com>,
	Marek Szyprowski <m.szyprowski@...sung.com>,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 0/5] mfd: Fix platform device ids to avoid probe
 failure

On Mon, Mar 23, 2015 at 02:11:50PM +0100, Bartlomiej Zolnierkiewicz wrote:
> On Monday, March 23, 2015 11:07:18 AM Johan Hovold wrote:
> > On Fri, Mar 20, 2015 at 08:23:18PM +0100, Bartlomiej Zolnierkiewicz wrote:
> > 
> > > Commit 6e3f62f0793e ("mfd: core: Fix platform-device id generation")
> > > changed the way platform device ids are generated from mfd id base and
> > > cell ids in mfd_add_device().  Unfortunately the change in question
> > > breaks mfd drivers which are using mfd_add_devices() with mfd id base
> > > equal to -1 and non-zero cell ids (used to distinguish cells with
> > > the same name field).  The result is that mfd core tries to register
> > > platform devices with the same name which obviously fails and leads
> > > to mfd device probe failure.
> > 
> > First of all, thanks for finding these. I obviously overlooked this
> > class of drivers when fixing the device-id generation.
> > 
> > > Changing mfd_add_devices() mfd id base from -1 to 0 and at the same
> > > time setting proper cell ids for all cells fixes the issue.
> > 
> > This is however not the right fix. Instead you should be using
> > PLATFORM_DEVID_AUTO and keep the non-zero cell-ids as is, as this will
> > allow more than one mfd-device to be registered without resorting to
> > hacks.
> 
> Conversion of a driver to use PLATFORM_DEVID_AUTO changes names of
> all platform devices registered by the driver.  In my patchset I just
> tried to restore the broken functionality (patch that broke it went
> in v3.19).  I thought that it was the best solution for v3.19 and
> v4.0-rc4 (then PLATFORM_DEVID_AUTO conversion can be done sometime
> later, i.e. in v4.1).

I think you're right. We should do the conversion to PLATFORM_DEVID_AUTO
later.

I'm responding to this mail with two patches for v4.0 fixing the da9052
driver, which is currently broken although not in the way suggested by
your v1-series, and the other drivers you identified by doing a partial
revert of commit 6e3f62f0793e ("mfd: core: Fix platform-device id
generation").

Thanks,
Johan
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