Re: [PATCH] i2c: i2c-scmi: add a MS HID

Re: [PATCH] i2c: i2c-scmi: add a MS HID

[Wolfram Sang]

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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.

> From: Edgar Cherkasov <echerkasov@dev.rtsoft.ru>
> 
> 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@dev.rtsoft.ru>
> Signed-off-by: Michael Brunner <Michael.Brunner@kontron.com>
> Acked-by: Viktor Krasnov <vkrasnov@dev.rtsoft.ru>
> ---
>  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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Re: [PATCH] i2c: i2c-scmi: add a MS HID

[Wolfram Sang]

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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@dev.rtsoft.ru>
> > 
> > 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@dev.rtsoft.ru>
> > Signed-off-by: Michael Brunner <Michael.Brunner@kontron.com>
> > Acked-by: Viktor Krasnov <vkrasnov@dev.rtsoft.ru>
> > ---
> >  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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Re: [PATCH] i2c: i2c-scmi: add a MS HID

[Mika Westerberg]

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@dev.rtsoft.ru>
> > > 
> > > 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@dev.rtsoft.ru>
> > > Signed-off-by: Michael Brunner <Michael.Brunner@kontron.com>
> > > Acked-by: Viktor Krasnov <vkrasnov@dev.rtsoft.ru>
> > > ---
> > >  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?

Re: [PATCH] i2c: i2c-scmi: add a MS HID

[Viktor Krasnov]

Hello Mika,

thanks for the review.

> > --- 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?

This has been done by analogy with existing ACPI_SMBUS_IBM_HID which is
defined in acpi_drivers.h. I think that it may look confusing when some
HIDs are defined in i2c-scmi.c and others - in acpi_drivers.h. Could you
please clarify this moment and confirm that all HIDs must be defined
only in i2c-scmi.c? I will rework the patch then.

Best regards,
Viktor Krasnov.

On Fri, 2017-03-31 at 10:20 +0300, Mika Westerberg wrote:
> 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@dev.rtsoft.ru>
> > > > 
> > > > 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@dev.rtsoft.ru>
> > > > Signed-off-by: Michael Brunner <Michael.Brunner@kontron.com>
> > > > Acked-by: Viktor Krasnov <vkrasnov@dev.rtsoft.ru>
> > > > ---
> > > >  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?

Re: [PATCH] i2c: i2c-scmi: add a MS HID

[Mika Westerberg]

On Fri, Mar 31, 2017 at 10:31:07AM +0300, Viktor Krasnov wrote:
> Hello Mika,
> 
> thanks for the review.
> 
> > > --- 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?
> 
> This has been done by analogy with existing ACPI_SMBUS_IBM_HID which is
> defined in acpi_drivers.h. I think that it may look confusing when some
> HIDs are defined in i2c-scmi.c and others - in acpi_drivers.h. Could you
> please clarify this moment and confirm that all HIDs must be defined
> only in i2c-scmi.c? I will rework the patch then.

If there is only one file using a HID, then I think it is fine to keep
it in the driver itself. If multiple files share the HID then it makes
sense to put it to include/acpi/acpi_drivers.h.

Re: [PATCH] i2c: i2c-scmi: add a MS HID

[Viktor Krasnov]

Hello Mika,

> If there is only one file using a HID, then I think it is fine to keep
> it in the driver itself. If multiple files share the HID then it makes
> sense to put it to include/acpi/acpi_drivers.h.

Understood, thanks for the detailed explanation. Indeed,
ACPI_SMBUS_IBM_HID is referenced in several files, so it explains why
this HID is defined in include/acpi/acpi_drivers.h and not in i2c-scmi.c
itself.

Ok, I will correct the patch, retest it and resend in next few days.

Best regards,
Viktor Krasnov.

On Fri, 2017-03-31 at 10:47 +0300, Mika Westerberg wrote:
> On Fri, Mar 31, 2017 at 10:31:07AM +0300, Viktor Krasnov wrote:
> > Hello Mika,
> > 
> > thanks for the review.
> > 
> > > > --- 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?
> > 
> > This has been done by analogy with existing ACPI_SMBUS_IBM_HID which is
> > defined in acpi_drivers.h. I think that it may look confusing when some
> > HIDs are defined in i2c-scmi.c and others - in acpi_drivers.h. Could you
> > please clarify this moment and confirm that all HIDs must be defined
> > only in i2c-scmi.c? I will rework the patch then.
> 
> If there is only one file using a HID, then I think it is fine to keep
> it in the driver itself. If multiple files share the HID then it makes
> sense to put it to include/acpi/acpi_drivers.h.

Re: [PATCH] i2c: i2c-scmi: add a MS HID

[Andy Shevchenko]

On Thu, 2017-03-30 at 17:52 +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:

> > > 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>


A bit of offtopic here, but I have noticed kontron.com address in SoB
lines.

I would like to know if Kontron will follow ACPI spec when assembling
firmwares for its board [1]?

Table name LPW8 for SSDT is not allowed by spec and can't be just
decompiled without hacking either table or decompiler.

[1] http://www.kontron.com/products/boards-and-standard-form-factors/sma
rc/smarc-sxbt.html

P.S. We may continue privately to not contaminate mailing list with
unnecessary noise.

-- 
Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Intel Finland Oy