linux-kernel - Re: char/tpm: tpm_infineon no longer loaded for HP 2510p laptop

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Message-Id: <200808200956.52883.bjorn.helgaas@hp.com>
Date:	Wed, 20 Aug 2008 09:56:52 -0600
From:	Bjorn Helgaas <bjorn.helgaas@...com>
To:	Frans Pop <elendil@...net.nl>
Cc:	linux-kernel@...r.kernel.org, Marcel Selhorst <tpm@...horst.net>,
	Kay Sievers <kay.sievers@...y.org>,
	Thomas Renninger <trenn@...e.de>,
	Adam Belay <ambx1@....rr.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	"Rafael J. Wysocki" <rjw@...k.pl>
Subject: Re: char/tpm: tpm_infineon no longer loaded for HP 2510p laptop

On Monday 18 August 2008 07:40:24 am Frans Pop wrote:
> While comparing the loaded modules for 2.6.26 and 2.6.27-rc3 for my HP 
> 2510p, I noticed that the tpm_infineon module and related modules no 
> longer get loaded automatically.
> 
> The difference seems to be that 2.6.26 listed:
> /lib/modules/2.6.26.2/modules.alias:alias pnp:dIFX0102* tpm_infineon
> /lib/modules/2.6.26.2/modules.alias:alias pnp:dIFX0101* tpm_infineon
> 
> while 2.6.27 has:
> /lib/modules/2.6.27-rc3/modules.alias:alias acpi*:IFX0101:* tpm_infineon
> /lib/modules/2.6.27-rc3/modules.alias:alias pnp:dIFX0101* tpm_infineon
> 
> My system has:
> $ grep IFX /sys/bus/pnp/devices/*/id
> /sys/bus/pnp/devices/00:02/id:IFX0102

drivers/char/tpm/tpm_infineon.c hasn't changed since v2.6.26.  I think
the problem is more likely related to commit 22454cb99fc39f2629a:
http://git.kernel.org/?p=linux/kernel/git/torvalds/linux-2.6.git;a=commitdiff;h=22454cb99fc39f2629ad06a7eccb3df312f8830e

I don't know enough about modaliases to understand the point of this
patch, but I am suspicious of this part of it:

-               do_table(symval, sym->st_size,
-                        sizeof(struct pnp_device_id), "pnp",
-                        do_pnp_entry, mod);
+               do_pnp_device_entry(symval, sym->st_size, mod);

That suggests to me that where we used to generate an alias for every
PNP ID in the table:

    static const struct pnp_device_id tpm_pnp_tbl[] = {
        {"IFX0101", 0},
        {"IFX0102", 0},
        {"", 0}
    };

possibly the new code only does it for the first entry (IFX0101).

Apart from problem Frans points out, I'd like to understand the reason
for generating the "acpi*" aliases for PNP drivers.  I'd like to move
away from ACPI being visible to userland, and this file2alias.c change
makes it *more* visible.

Bjorn
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