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"
> >
> > /*
> > * For fixed hardware buttons, we fabricate acpi_devices with HID
> > --
> > 1.9.3
> >
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