On Wed, 1 Dec 2010 14:14:22 -0200
Herton Ronaldo Krzesinski <herton@xxxxxxxxxxxxxxx> wrote:
> Hi,
>
> > > +static acpi_status wmi_setget_mtd(struct shuttle_cmd *scmd, u32 **res)
> > > +{
> > > + Â Â Â acpi_status status;
> > > + Â Â Â union acpi_object *obj;
> > > + Â Â Â struct acpi_buffer input;
> > > + Â Â Â static DEFINE_MUTEX(mtd_lock);
> > > + Â Â Â struct acpi_buffer output = { ACPI_ALLOCATE_BUFFER, NULL };
> > > +
> > > + Â Â Â input.length = sizeof(struct shuttle_cmd);
> > > + Â Â Â scmd->hdr = 0xec00;
> > > + Â Â Â input.pointer = (u8 *) scmd;
> > > +
> > > + Â Â Â mutex_lock(&mtd_lock);
> > > + Â Â Â status = wmi_evaluate_method(SHUTTLE_WMI_SETGET_GUID, 0, 2,
> > > + Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â&input, &output);
> > > + Â Â Â mutex_unlock(&mtd_lock);
> >
> > I'm not sure why you need a mutex here ?
>
> I need mutex because of the way the vendor implemented things in its wmi
> interface. If I don't serialize the access to it, when sending commands
> in parallel some of them will fail, for example:
>
> # echo 1 > webcam & rfkill unblock <idx> & echo 1 > touchpad
>
> some of the echos or rfkill will fail. This happens because the vendor used a
> common buffer/variable to store parameters in AML code, from the DSDT:
>
> Name (AC00, Buffer (0x28)
> ...
> CreateDWordField (AC00, Zero, SAC0)
> CreateDWordField (AC00, 0x04, SAC1)
> ...
> CreateByteField (AC00, Zero, SA00)
> CreateByteField (AC00, One, SA01)
> CreateByteField (AC00, 0x02, SA02)
> CreateByteField (AC00, 0x03, SA03)
> CreateByteField (AC00, 0x04, SA04)
> ...
> Method (WMBC, 3, NotSerialized)
> {
> If (LEqual (Arg1, One))
> {
> Return (GETC (Arg0))
> }
>
> If (LEqual (Arg1, 0x02))
> {
> Return (SETC (Arg0, Arg2))
> }
> ...
> Method (SETC, 2, NotSerialized)
> {
> If (LEqual (Arg0, Zero))
> {
> Store (Arg1, AC00)
> OEMF (AC00)
> Return (SAC0)
> }
> ...
> Method (OEMF, 1, NotSerialized)
> {
> If (LEqual (SAC1, 0xEC000300))
> {
> Store (0x73, DBG8)
> Store ("LS", SAC0)
> Return (SAC0)
> }
>
> If (LEqual (SAC1, 0xEC000000))
> {
> WKBC (SA00, SA01, SA02, SA03)
> Return (SAC0)
> }
> ...
>
>
> Note that it uses only buffer AC00 to store and read the
> parameters, so parallel calls will overwrite the value in AC00
> (referenced as SAC?? and SA?? in some places) and some commands
> will fail or have unpredicted behaviour.
>
> Placing the lock prevents the parallel echo/rfkill command I placed
> above as example to fail, all writes/commands are sent successfuly.
>
> I'm attaching here DSDT of both machines I have for you to see the
> entire code.
Too long reply and forgot to attach it :P
here it goes the two gzipped.
--
[]'s
Herton
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