Messages in this thread | | | From | "Moore, Robert" <> | Subject | RE: [PATCH] ACPICA: Export mutex functions | Date | Mon, 17 Apr 2017 20:40:38 +0000 |
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> -----Original Message----- > From: Guenter Roeck [mailto:linux@roeck-us.net] > Sent: Monday, April 17, 2017 12:45 PM > To: Moore, Robert <robert.moore@intel.com> > Cc: Zheng, Lv <lv.zheng@intel.com>; Wysocki, Rafael J > <rafael.j.wysocki@intel.com>; 'Len Brown' <lenb@kernel.org>; 'linux- > acpi@vger.kernel.org' <linux-acpi@vger.kernel.org>; 'devel@acpica.org' > <devel@acpica.org>; 'linux-kernel@vger.kernel.org' <linux- > kernel@vger.kernel.org>; Box, David E <david.e.box@intel.com> > 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@roeck-us.net>; Zheng, Lv > > > <lv.zheng@intel.com> > > > Cc: Wysocki, Rafael J <rafael.j.wysocki@intel.com>; Len Brown > > > <lenb@kernel.org>; linux-acpi@vger.kernel.org; devel@acpica.org; > > > linux- kernel@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 > > > [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 > >
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