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

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Message-ID: <BFC9031E-E471-4EF6-832C-D6E05E2AAAC2@gmx.de>
Date:	Tue, 01 Dec 2015 10:26:17 -0800
From:	Peter Huewe <peterhuewe@....de>
To:	Jason Gunthorpe <jgunthorpe@...idianresearch.com>,
	"Wilck, Martin" <martin.wilck@...fujitsu.com>
CC:	"tpmdd-devel@...ts.sourceforge.net" 
	<tpmdd-devel@...ts.sourceforge.net>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Uwe Kleine-König 
	<u.kleine-koenig@...gutronix.de>
Subject: Re: [tpmdd-devel] [PATCH] base/platform: fix panic when probe function is NULL



Am 1. Dezember 2015 09:25:37 PST, schrieb Jason Gunthorpe <jgunthorpe@...idianresearch.com>:
>On Tue, Dec 01, 2015 at 04:19:25PM +0100, Wilck, Martin wrote:
>> > > > tpm_tis_init calls tpmm_chip_alloc which barfs when pdev (i.e.
>the return value
>> > > > of platform_device_register_simple above) isn't bound. It is
>not allowed
>> > > > to assume that the device is bound after the above function
>calls.
>> > > 
>> > > Can you please explain again why you think that assumption is
>invalid? 
>> > 
>> > You can unbind a device from a driver via sysfs, you can also
>prevent
>> > binding somehow I think, probing can fail for different reasons,
>probing
>> > might wait for userspace interaction to load firmware which wasn't
>> > scheduled yet. I'm sure there are still more things that break the
>> > assumption.
>> 
>> Thanks. Out of these, "prevent binding somehow" would be the only
>> problem that applies to tpm_tis, as probing can't fail (no probe()
>> routine), there's no FW to load, and unbinding via sysfs would
>require
>> nearly impossible timing (not sure if it could be done with udev).
>> 
>> Anyway, the Right Thing to do is to create a probe() routine and
>that's
>> what Jason did.
>
>That fixes tpm_tis, but there are other ancient TPM drivers that use
>the old, now broken way.
>
>So, we still need to do something here. Either fixup b8b2c7d845d5 as
>you have proposed, remove the now broken obsolete TPM drivers, or try
>and fix them..

How broken are they and since when?

I thought multiple times about deprecating and finally removing the 1.1b stuff - tpm 1.2 is out for 10? years now? With an expected life span of a TPM of roughly 5years... 
And also unfortunately the 1.1b legacy drivers usually get loaded first :( (atleast for slb9635)

Mark them as obsolete , default them to No and remove them by 4.10 if there are no objections?

Peter
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