On Mon, Apr 17, 2017 at 08:40:38PM +0000, Moore, Robert wrote: > > > > -----Original Message----- > > From: Guenter Roeck [mailto:li...@roeck-us.net] > > Sent: Monday, April 17, 2017 12:45 PM > > To: Moore, Robert <robert.mo...@intel.com> > > Cc: Zheng, Lv <lv.zh...@intel.com>; Wysocki, Rafael J > > <rafael.j.wyso...@intel.com>; 'Len Brown' <l...@kernel.org>; 'linux- > > a...@vger.kernel.org' <linux-a...@vger.kernel.org>; 'de...@acpica.org' > > <de...@acpica.org>; 'linux-kernel@vger.kernel.org' <linux- > > ker...@vger.kernel.org>; Box, David E <david.e....@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 <li...@roeck-us.net>; Zheng, Lv > > > > <lv.zh...@intel.com> > > > > Cc: Wysocki, Rafael J <rafael.j.wyso...@intel.com>; Len Brown > > > > <l...@kernel.org>; linux-a...@vger.kernel.org; de...@acpica.org; > > > > linux- ker...@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). >
I did. However, not being an ACPI expert, that doesn't tell me anything. Guenter > > > > > > > > > > > Other than this case, the OS/drivers should never need to directly > > acquire an AML mutex. > > > Bob > > >
