linux-kernel - Re: [PATCH 2/2] PNP: Unbind drivers if the new driver matches _HID rather than

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Message-ID: <20120925192211.GA24750@srcf.ucam.org>
Date:	Tue, 25 Sep 2012 20:22:11 +0100
From:	Matthew Garrett <mjg59@...f.ucam.org>
To:	Bjorn Helgaas <bhelgaas@...gle.com>
Cc:	gregkh@...uxfoundation.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 2/2] PNP: Unbind drivers if the new driver matches _HID
 rather than _CID

On Tue, Sep 25, 2012 at 01:04:25PM -0600, Bjorn Helgaas wrote:
> On Tue, Sep 25, 2012 at 7:25 AM, Matthew Garrett <mjg@...hat.com> wrote:

> Do you know of any scenarios besides this IPMI one where there's the
> possibility of two drivers matching the same device?  If so, does the
> detach/attach process work reasonably?  My worry is that drivers don't
> normally give up devices, so the detach path is not well exercised.
> And I don't know what happens to any users of the device during the
> switch.  For example, if something was using a TPM and we replaced the
> driver, what does that look like to the user?

Yeah, this could definitely happen with TPM - tpm_infinion could 
displace tpm_tis. This actually flags up something kind of obviously 
broken in the TPM code, since tpm_infineon comes *after* tpm_tis in the 
link order despite being more specific. Winning. It looks like there's a 
valid tpm_release function, but I'll find an infineon machine and figure 
out whether it actually works or not.

-- 
Matthew Garrett | mjg59@...f.ucam.org
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