linux-kernel - I/O collisions w/ hwmon/it87.c and watchdog/it8712f

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Message-ID: <76366b180802101304j359e2873vd9dd974920bf6745@mail.gmail.com>
Date:	Sun, 10 Feb 2008 16:04:25 -0500
From:	"Andrew Paprocki" <andrew@...iboo.com>
To:	linux-kernel@...r.kernel.org
Cc:	"Jorge Boncompte" <jorge@...2.net>,
	"Jean Delvare" <khali@...ux-fr.org>,
	"Chris Gauthron" <chrisg@...n.com>
Subject: I/O collisions w/ hwmon/it87.c and watchdog/it8712f_wdt.c? (Super I/O chips in general..)

I'm interested in expanding the current support for the it87 Super I/O
chip to provide access to more of its capabilities. I started by
looking at two existing drivers which talk to different parts of the
chip. Maybe I'm missing something, but what guarantees that both of
these drivers won't attempt to talk to the chip at the same time?

The watchdog/it8712f_wdt.c driver has an internal spinlock, the
hwmon/it87.c driver doesn't, and I don't see how a lock could be
shared across both unless it is taken care of at a lower level that
I'm not aware of. You can see that code is essentially copied between
the two files to talk to the chip.

This brings me to a more general question regarding SuperI/O chips.
Since these chips touch many different parts of traditionally separate
driver areas, how should the drivers be structured so that they can
all talk to the chip? Should the low level communications routines for
the chip live in a library which all the drivers could use? Should all
of the created devices live inside one file? (e.g. platform/it87.c
instead of hwmon, watchdog, etc)

Thanks,
-Andrew
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