From: Guenter Roeck [mailto:[email protected]] Sent: Tuesday, April 18, 2017 3:45 AM 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 <linux(a)roeck-us.net&gt;; Zheng, Lv <lv.zheng(a)intel.com&gt; > > Cc: Wysocki, Rafael J <rafael.j.wysocki(a)intel.com&gt;; Len Brown > > <lenb(a)kernel.org&gt;; linux-acpi(a)vger.kernel.org; devel(a)acpica.org; linux- > > kernel(a)vger.kernel.org > > 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 > > > > Other than this case, the OS/drivers should never need to directly acquire an AML mutex. > Bob >