On Wed, 13 Apr 2011 01:05:33 -0700, Natarajan Gurumoorthy wrote: > Hans, > Comments below > > On Tue, Apr 12, 2011 at 11:50 PM, Hans de Goede <hdegoede@xxxxxxxxxx> wrote: > > > > You shouldn't (void) this, there is a reason you get a warning > > otherwise! request_muxed_region can still fail if some other driver > > has done a none muxed request_region on the same region, and in that > > case you should not continue with accessing the io-ports. > There are 3 it87 drivers and they all have to do the exact same > sequence to put the chip into a mode where they can modify its state. > The sequences involve non atomic sequences that write locations 0x2e > and 0x2f. When they are done they write a different sequence to these > 2 locations. The entry routine is superio_enter and exit is > superio_exit. All the it87 drivers reserve these 2 locations before > they start manipulating the chip. This macro will hold off requestors > if the resource is busy because one of the other drivers is > manipulating the chip. Once the an it87 driver is done it calls > superio_exit which will release the reservation on those 2 locations > letting any other driver on the wait queue to now gain access two > locations. > > Please read code in kernel/resource.c function "__request_region". > "request_muxed_region" turns on IORESOURCE_MUXED bit and that means > that only way an it87 driver will get back from a call to > "request_muxed_region" is when it gets hold of the region. > > The scenario you mention above can never happen. Let me be straight clear, as apparently you have difficulties understanding Hans's simple request: You do not get to (void) the return of request_muxed_region(), period. This is _not_ negotiable. What other it87 drivers currently in the tree do or don't do is totally irrelevant. There can be new it87 drivers added later, there can be out-of-tree it87 drivers (including old copies of in-tree ones), and there can be non-it87 drivers accessing the I/O ports (or at least attempting to.) So the scenario mentioned by Hans can very well happen, and you have to deal with it. Thanks, -- Jean Delvare _______________________________________________ lm-sensors mailing list lm-sensors@xxxxxxxxxxxxxx http://lists.lm-sensors.org/mailman/listinfo/lm-sensors
