On Thu, Mar 30, 2017 at 05:52:33PM +0200, Wolfram Sang wrote:
> On Thu, Mar 23, 2017 at 09:47:47PM +0100, Wolfram Sang wrote:
> > On Fri, Mar 10, 2017 at 04:58:35PM +0300, Viktor Krasnov wrote:
> >
> > Thanks for the patch!
> >
> > adding linux-acpi to CC. This is more an ACPI question than I2C.
>
> Mika? Andy? Jarkko? Any input on this?
>
> >
> > > From: Edgar Cherkasov <echerkasov@xxxxxxxxxxxxx>
> > >
> > > Description of the problem:
> > > - i2c-scmi driver contains only two identifiers "SMBUS01" and "SMBUSIBM";
> > > - the fist HID (SMBUS01) is clearly defined in "SMBus Control Method
> > > Interface Specification, version 1.0": "Each device must specify
> > > 'SMBUS01' as its _HID and use a unique _UID value";
> > > - unfortunately, BIOS vendors (like AMI) seem to ignore this requirement
> > > and implement "SMB0001" HID instead of "SMBUS01";
> > > - I speculate that they do this because only "SMB0001" is hard coded in
> > > Windows SMBus driver produced by Microsoft.
> > >
> > > This leads to following situation:
> > > - SMBus works out of box in Windows but not in Linux;
> > > - board vendors are forced to add correct "SMBUS01" HID to BIOS to make
> > > SMBus work in Linux. Moreover the same board vendors complain that
> > > tools (3-rd party ASL compiler) do not like the "SMBUS01" identifier
> > > and produce errors. So they need to constantly patch the compiler for
> > > each new version of BIOS.
> > >
> > > As it is very unlikely that BIOS vendors implement a correct HID in
> > > future, I would propose to consider whether it is possible to work around
> > > the problem by adding MS HID to the Linux i2c-scmi driver.
> > >
> > > Signed-off-by: Edgar Cherkasov <echerkasov@xxxxxxxxxxxxx>
> > > Signed-off-by: Michael Brunner <Michael.Brunner@xxxxxxxxxxx>
> > > Acked-by: Viktor Krasnov <vkrasnov@xxxxxxxxxxxxx>
> > > ---
> > > drivers/i2c/busses/i2c-scmi.c | 1 +
> > > include/acpi/acpi_drivers.h | 2 ++
> > > 2 files changed, 3 insertions(+)
> > >
> > > diff --git a/drivers/i2c/busses/i2c-scmi.c b/drivers/i2c/busses/i2c-scmi.c
> > > index dfc98df..fb9aee0 100644
> > > --- a/drivers/i2c/busses/i2c-scmi.c
> > > +++ b/drivers/i2c/busses/i2c-scmi.c
> > > @@ -51,6 +51,7 @@ struct acpi_smbus_cmi {
> > > static const struct acpi_device_id acpi_smbus_cmi_ids[] = {
> > > {"SMBUS01", (kernel_ulong_t)&smbus_methods},
> > > {ACPI_SMBUS_IBM_HID, (kernel_ulong_t)&ibm_smbus_methods},
> > > + {ACPI_SMBUS_MS_HID, (kernel_ulong_t)&smbus_methods},
> > > {"", 0}
> > > };
> > > MODULE_DEVICE_TABLE(acpi, acpi_smbus_cmi_ids);
> > > diff --git a/include/acpi/acpi_drivers.h b/include/acpi/acpi_drivers.h
> > > index 29c6912..d34538b 100644
> > > --- a/include/acpi/acpi_drivers.h
> > > +++ b/include/acpi/acpi_drivers.h
> > > @@ -60,6 +60,8 @@
> > > #define ACPI_DOCK_HID "LNXDOCK"
> > > /* Quirk for broken IBM BIOSes */
> > > #define ACPI_SMBUS_IBM_HID "SMBUSIBM"
> > > +/* SMBUS HID definition as supported by Microsoft Windows */
> > > +#define ACPI_SMBUS_MS_HID "SMB0001"
I agree with the reasoning but why do you add the ID here also? Wouldn't
it suffice if added only to the i2c-scmi.c driver?
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