4.4-stable review patch. If anyone has any objections, please let me know.
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From: Edgar Cherkasov echerkasov@dev.rtsoft.ru
[ Upstream commit e058e7a4bc89104540a8a303682248614b5df6f1 ]
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@dev.rtsoft.ru Signed-off-by: Michael Brunner Michael.Brunner@kontron.com Acked-by: Viktor Krasnov vkrasnov@dev.rtsoft.ru Reviewed-by: Jean Delvare jdelvare@suse.de Reviewed-by: Mika Westerberg mika.westerberg@linux.intel.com Signed-off-by: Wolfram Sang wsa@the-dreams.de Signed-off-by: Sasha Levin alexander.levin@microsoft.com Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- drivers/i2c/busses/i2c-scmi.c | 4 ++++ 1 file changed, 4 insertions(+)
--- 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 @@ static const struct smbus_methods_t ibm_ 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);