Date: Sat, 28 Nov 2015 18:40:03 +0200
From: Jarkko Sakkinen <jarkko.sakkinen@linux.intel.com>
To: Jason Gunthorpe <jgunthorpe@obsidianresearch.com>
Cc: martin.wilck@ts.fujitsu.com, gregkh@linuxfoundation.org,
        tpmdd-devel@lists.sourceforge.net, linux-kernel@vger.kernel.org,
        u.kleine-koenig@pengutronix.de
Subject: Re: [tpmdd-devel] [PATCH] base/platform: fix panic when probe
 function is NULL
Message-ID: <20151128164003.GE6518@intel.com>
References: <1448564494-23218-1-git-send-email-martin.wilck@ts.fujitsu.com>
 <20151126203031.GA1139@obsidianresearch.com>
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On Thu, Nov 26, 2015 at 01:30:31PM -0700, Jason Gunthorpe wrote:
> On Thu, Nov 26, 2015 at 08:01:34PM +0100, martin.wilck@ts.fujitsu.com wrote:
> > From: Martin Wilck <Martin.Wilck@ts.fujitsu.com>
> > 
> > Since b8b2c7d845d5, platform_drv_probe() is called for all platform
> > devices. If drv->probe is NULL, and dev_pm_domain_attach() fails,
> > platform_drv_probe() will return the error code from dev_pm_domain_attach().
> > 
> > This causes real_probe() to enter the "probe_failed" path and set
> > dev->driver to NULL. Before b8b2c7d845d5, real_probe() would assume
> > success if both dev->bus->probe and drv->probe are missing.
> > 
> > This may cause a panic later. For example, inserting the tpm_tis
> > driver with parameter "force=1" (i.e. registering tpm_tis as a platform
> > driver) will panic in tpmm_chip_alloc() because dev->driver is NULL:
> > 
> >      chip->cdev.owner = chip->pdev->driver->owner;
> 
> Is this happening because tpm_tis is not creating the platform device
> properly? ie it just calls platform_device_register_simple and then
> force initializes it via tpm_tis_init, which expects to be called from
> a probe function with an attached driver.

Agreed. We should have a probe callback.

> Instead we should setup a proper platform device with the default
> IO range for x86 and let the driver core call tpm_tis_init via
> tis_drv.probe.
> 
> Would changing things in this way fix the problem you've observed?
> 
> I have some patches to do this that are part of my OF enablement
> series, but I can make something simpler that would deal with this
> fairly quickly if you can test.

Does the patch set that you sent include the fix or not? I haven't yet
reviewed them properly.

> Jason

/Jarkko
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