On Sat, Jun 09, 2012 at 10:39:46AM -0400, Mark Fortescue wrote: > Hi All, > > I have recently noticed a flaw in the design of linux drivers for SuperIO > chips. > > I have a dual core board with two SuperIO chips. > > Winbond W83627DFG: watchdog/w83627hf_wdt, hwmon/w83627ehf > Fintek F81216: > > The existing driver for the currently supported SuperIO chip is split > into two kernel modules each with its own private IO lock. > > If I continue this model and implement drivers to use the Fintek F81216 > watchdog and the Winbond W83627DFG GPIO then I end up with more private IO > locks and more potential to get a clash when two or more drivers are > trying to access the same ports at the same time. > > What is needed for SuperIO chips is a common way of locking the port > resource while the SuperIO chip is being accessed. A single common io_lock > would be the first and simplest approach. This is at least safe unlike the > current situation. > > A better and longer term solution would be to update all the affected > drivers to use the existing recource allocation system for the SuperIO > ports (usually 0x2E/2F and 0x4E/4F) to reserve the port while it is in > use. > > If this is considered too slow/complex and/or too much work then an > alternative SuperIO port locking system may be need that dynamically > provides locks for a specified SuperIO port address. A driver for a > SuperIO chip would request a lock for the desired port address during > initialisation and free it up on exit. If scanning for a SuperIO chip, > the port lock would be requested and then freed for each port scanned, > untill the IO chip is located. This would involve minimal changes > to the existing drivers without single treading access to SuperIO chips on > different ports. > Some drivers already implement superio memory region locking (it87, f71882fg, sch56xx). Is this what you are looking for ? Thanks, Guenter > If any of you think that this needs a wider ordiance, please forward to > the appropriate mailing lists. > > Please CC me on any followups. > > Regards > Mark Fortescue. > > mark @ mtfhpc . demon . co . uk > > _______________________________________________ > lm-sensors mailing list > lm-sensors@xxxxxxxxxxxxxx > http://lists.lm-sensors.org/mailman/listinfo/lm-sensors -- To unsubscribe from this list: send the line "unsubscribe linux-watchdog" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
