| Message ID | 20231103185716.11007-9-W_Armin@gmx.de (mailing list archive) |
|---|---|
| State | Superseded |
| Headers | show |
| Series | hwmon: (dell-smm) Add support for WMI SMM interface | expand |
On Fri, Nov 03, 2023 at 07:57:15PM +0100, Armin Wolf wrote: > Document the WMI SMM interface so that future developers > can better understand how it works. > > Signed-off-by: Armin Wolf <W_Armin@gmx.de> > --- > Documentation/hwmon/dell-smm-hwmon.rst | 33 +++++++++++++++++++++++--- > 1 file changed, 30 insertions(+), 3 deletions(-) > > diff --git a/Documentation/hwmon/dell-smm-hwmon.rst b/Documentation/hwmon/dell-smm-hwmon.rst > index d8f1d6859b96..fea8cf76088e 100644 > --- a/Documentation/hwmon/dell-smm-hwmon.rst > +++ b/Documentation/hwmon/dell-smm-hwmon.rst > @@ -186,8 +186,7 @@ SMM Interface > The driver uses the SMM interface to send commands to the system BIOS. > This interface is normally used by Dell's 32-bit diagnostic program or > on newer notebook models by the buildin BIOS diagnostics. > -The SMM is triggered by writing to the special ioports ``0xb2`` and ``0x84``, > -and may cause short hangs when the BIOS code is taking too long to > +The SMM may cause short hangs when the BIOS code is taking too long to > execute. > > The SMM handler inside the system BIOS looks at the contents of the > @@ -210,7 +209,35 @@ The SMM handler can signal a failure by either: > > - setting the lower sixteen bits of ``eax`` to ``0xffff`` > - not modifying ``eax`` at all > -- setting the carry flag > +- setting the carry flag (legacy SMM interface only) > + > +Legacy SMM Interface > +-------------------- > + > +When using the legacy SMM interface, a SMM is triggered by writing the least significant byte > +of the command code to the special ioports ``0xb2`` and ``0x84``. This interface is not > +described inside the ACPI tables and can thus only be detected by issuing a test SMM call. > + > +WMI SMM Interface > +----------------- > + > +On modern Dell machines, the SMM calls are done over ACPI WMI: > + > +:: > + > + #pragma namespace("\\\\.\\root\\dcim\\sysman\\diagnostics") > + [WMI, Provider("Provider_DiagnosticsServices"), Dynamic, Locale("MS\\0x409"), Description("RunDellDiag"), guid("{F1DDEE52-063C-4784-A11E-8A06684B9B01}")] > + class LegacyDiags { > + [key, read] string InstanceName; > + [read] boolean Active; > + > + [WmiMethodId(1), Implemented, read, write, Description("Legacy Method ")] void Execute([in, out] uint32 EaxLen, [in, out, WmiSizeIs("EaxLen") : ToInstance] uint8 EaxVal[], [in, out] uint32 EbxLen, [in, out, WmiSizeIs("EbxLen") : ToInstance] uint8 EbxVal[], [in, out] uint32 EcxLen, [in, out, WmiSizeIs("EcxLen") : ToInstance] uint8 EcxVal[], [in, out] uint32 EdxLen, [in, out, WmiSizeIs("EdxLen") : ToInstance] uint8 EdxVal[]); I don't think this has to violate formatting rules. Guenter > + }; > + > +Some machines support only the WMI SMM interface, while some machines support both interfaces. > +The driver automatically detects which interfaces are present and will use the WMI SMM interface > +if the legacy SMM interface is not present. The WMI SMM interface is usually slower than the > +legacy SMM interface since ACPI methods need to be called in order to trigger a SMM. > > SMM command codes > ----------------- > -- > 2.39.2 >
diff --git a/Documentation/hwmon/dell-smm-hwmon.rst b/Documentation/hwmon/dell-smm-hwmon.rst index d8f1d6859b96..fea8cf76088e 100644 --- a/Documentation/hwmon/dell-smm-hwmon.rst +++ b/Documentation/hwmon/dell-smm-hwmon.rst @@ -186,8 +186,7 @@ SMM Interface The driver uses the SMM interface to send commands to the system BIOS. This interface is normally used by Dell's 32-bit diagnostic program or on newer notebook models by the buildin BIOS diagnostics. -The SMM is triggered by writing to the special ioports ``0xb2`` and ``0x84``, -and may cause short hangs when the BIOS code is taking too long to +The SMM may cause short hangs when the BIOS code is taking too long to execute. The SMM handler inside the system BIOS looks at the contents of the @@ -210,7 +209,35 @@ The SMM handler can signal a failure by either: - setting the lower sixteen bits of ``eax`` to ``0xffff`` - not modifying ``eax`` at all -- setting the carry flag +- setting the carry flag (legacy SMM interface only) + +Legacy SMM Interface +-------------------- + +When using the legacy SMM interface, a SMM is triggered by writing the least significant byte +of the command code to the special ioports ``0xb2`` and ``0x84``. This interface is not +described inside the ACPI tables and can thus only be detected by issuing a test SMM call. + +WMI SMM Interface +----------------- + +On modern Dell machines, the SMM calls are done over ACPI WMI: + +:: + + #pragma namespace("\\\\.\\root\\dcim\\sysman\\diagnostics") + [WMI, Provider("Provider_DiagnosticsServices"), Dynamic, Locale("MS\\0x409"), Description("RunDellDiag"), guid("{F1DDEE52-063C-4784-A11E-8A06684B9B01}")] + class LegacyDiags { + [key, read] string InstanceName; + [read] boolean Active; + + [WmiMethodId(1), Implemented, read, write, Description("Legacy Method ")] void Execute([in, out] uint32 EaxLen, [in, out, WmiSizeIs("EaxLen") : ToInstance] uint8 EaxVal[], [in, out] uint32 EbxLen, [in, out, WmiSizeIs("EbxLen") : ToInstance] uint8 EbxVal[], [in, out] uint32 EcxLen, [in, out, WmiSizeIs("EcxLen") : ToInstance] uint8 EcxVal[], [in, out] uint32 EdxLen, [in, out, WmiSizeIs("EdxLen") : ToInstance] uint8 EdxVal[]); + }; + +Some machines support only the WMI SMM interface, while some machines support both interfaces. +The driver automatically detects which interfaces are present and will use the WMI SMM interface +if the legacy SMM interface is not present. The WMI SMM interface is usually slower than the +legacy SMM interface since ACPI methods need to be called in order to trigger a SMM. SMM command codes -----------------
Document the WMI SMM interface so that future developers can better understand how it works. Signed-off-by: Armin Wolf <W_Armin@gmx.de> --- Documentation/hwmon/dell-smm-hwmon.rst | 33 +++++++++++++++++++++++--- 1 file changed, 30 insertions(+), 3 deletions(-) -- 2.39.2