Re: [tpmdd-devel] [PATCH] base/platform: fix panic when probe function is NULL

[Jason Gunthorpe <jgunthorpe@obsidianresearch.com>]

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.

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.

Jason