On Tue, 4 Apr 2017 19:18:27 +0300, Viktor Krasnov wrote:
> 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.
>
> v2: move the definition of the new HID to the driver itself.
>
> Signed-off-by: Edgar Cherkasov <echerkasov@xxxxxxxxxxxxx>
> Signed-off-by: Michael Brunner <Michael.Brunner@xxxxxxxxxxx>
> Acked-by: Viktor Krasnov <vkrasnov@xxxxxxxxxxxxx>
Reviewed-by: Jean Delvare <jdelvare@xxxxxxx>
> ---
> drivers/i2c/busses/i2c-scmi.c | 4 ++++
> 1 file changed, 4 insertions(+)
>
> diff --git a/drivers/i2c/busses/i2c-scmi.c b/drivers/i2c/busses/i2c-scmi.c
> index dfc98df..f876dd6 100644
> --- a/drivers/i2c/busses/i2c-scmi.c
> +++ b/drivers/i2c/busses/i2c-scmi.c
> @@ -18,6 +18,9 @@
> #define ACPI_SMBUS_HC_CLASS "smbus"
> #define ACPI_SMBUS_HC_DEVICE_NAME "cmi"
>
> +/* SMBUS HID definition as supported by Microsoft Windows */
> +#define ACPI_SMBUS_MS_HID "SMB0001"
> +
> ACPI_MODULE_NAME("smbus_cmi");
>
> struct smbus_methods_t {
> @@ -51,6 +54,7 @@ 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);
--
Jean Delvare
SUSE L3 Support
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