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Message-ID: <20080211094051.147ce36f@hyperion.delvare> Date: Mon, 11 Feb 2008 09:40:51 +0100 From: Jean Delvare <khali@...ux-fr.org> To: "Andrew Paprocki" <andrew@...iboo.com> Cc: linux-kernel@...r.kernel.org, "Jorge Boncompte" <jorge@...2.net>, Jim Cromie <jim.cromie@...il.com>, Hans de Goede <j.w.r.degoede@....nl> Subject: Re: I/O collisions w/ hwmon/it87.c and watchdog/it8712f_wdt.c? (Super I/O chips in general..) Hi Andrew, On Sun, 10 Feb 2008 16:04:25 -0500, Andrew Paprocki wrote: > 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? Nothing guarantees it in general. However, at least most hwmon drivers avoid accessing the Super-I/O configuration space after driver initialization, which happens when the module is loaded. As module loading is serialized, this limits the risk of concurrent access. This is however a limitation I'd be happy to get rid of. It would be nice to be able to access some configuration space registers at run-time (e.g. VID readings). > 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) You probably want to discuss this with Jim Cromie and Hans de Goede (Cc'd.) They have been discussing a possible implementation in October 2007 on the lm-sensors list: http://lists.lm-sensors.org/pipermail/lm-sensors/2007-October/021561.html http://lists.lm-sensors.org/pipermail/lm-sensors/2007-October/021562.html http://lists.lm-sensors.org/pipermail/lm-sensors/2007-October/021563.html http://lists.lm-sensors.org/pipermail/lm-sensors/2007-October/021564.html http://lists.lm-sensors.org/pipermail/lm-sensors/2007-October/021565.html http://lists.lm-sensors.org/pipermail/lm-sensors/2007-October/021566.html -- Jean Delvare -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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