> -----Original Message----- > From: Guenter Roeck [mailto:[email protected]] > Sent: Monday, April 17, 2017 12:45 PM > To: Moore, Robert <[email protected]> > Cc: Zheng, Lv <[email protected]>; Wysocki, Rafael J > <[email protected]>; 'Len Brown' <[email protected]>; 'linux- > [email protected]' <[email protected]>; '[email protected]' > <[email protected]>; '[email protected]' <linux- > [email protected]>; Box, David E <[email protected]> > Subject: Re: [PATCH] ACPICA: Export mutex functions > > On Mon, Apr 17, 2017 at 07:27:37PM +0000, Moore, Robert wrote: > > > > > -----Original Message----- > > > From: Moore, Robert > > > Sent: Monday, April 17, 2017 10:13 AM > > > To: Guenter Roeck <[email protected]>; Zheng, Lv > > > <[email protected]> > > > Cc: Wysocki, Rafael J <[email protected]>; Len Brown > > > <[email protected]>; [email protected]; [email protected]; > > > linux- [email protected] > > > Subject: RE: [PATCH] ACPICA: Export mutex functions > > > > > > There is a model for the drivers to directly acquire an AML mutex > > > object. That is why the acquire/release public interfaces were added > > > to ACPICA. > > > > > > I forget all of the details, but the model was developed with MS and > > > others during the ACPI 6.0 timeframe. > > > > > > > > [Moore, Robert] > > > > > > Here is the case where the OS may need to directly acquire an AML > mutex: > > > > From the ACPI spec: > > > > 19.6.2 Acquire (Acquire a Mutex) > > > > Note: For Mutex objects referenced by a _DLM object, the host OS may > also contend for ownership. > > > From the context in the dsdt, and from description of expected use cases > for _DLM objects I can find, this is what the mutex is used for (to > serialize access to a resource on a low pin count serial interconnect, > aka LPC). > > What does that mean in practice ? That I am not supposed to use it > because it doesn't follow standard ACPI mutex declaration rules ? > > Thanks, > Guenter > > > [Moore, Robert]
I'm not an expert on the _DLM method, but I would point you to the description section in the ACPI spec, 5.7.5 _DLM (DeviceLock Mutex). > > > > > > Other than this case, the OS/drivers should never need to directly > acquire an AML mutex. > > Bob > >
