Much removed to cut down the size on this and to highlight a couple of specific sections pertinent to the ACPI on ARMv8 TODO List..... On 02/02/2015 05:45 AM, Hanjun Guo wrote: > From: Al Stone <al.stone@xxxxxxxxxx> > > Two more documentation files are also being added: > (1) A verbatim copy of the "Why ACPI on ARM?" blog posting by Grant Likely, > which is also summarized in arm-acpi.txt, and > > (2) A section by section review of the ACPI spec (acpi_object_usage.txt) > to note recommendations and prohibitions on the use of the numerous > ACPI tables and objects. This sets out the current expectations of > the firmware by Linux very explicitly (or as explicitly as I can, for > now). > > CC: Suravee Suthikulpanit <Suravee.Suthikulpanit@xxxxxxx> > CC: Yi Li <phoenix.liyi@xxxxxxxxxx> > CC: Mark Langsdorf <mlangsdo@xxxxxxxxxx> > CC: Ashwin Chaugule <ashwinc@xxxxxxxxxxxxxx> > Signed-off-by: Al Stone <al.stone@xxxxxxxxxx> > Signed-off-by: Hanjun Guo <hanjun.guo@xxxxxxxxxx> > --- > Documentation/arm64/acpi_object_usage.txt | 592 ++++++++++++++++++++++++++++++ > Documentation/arm64/why_use_acpi.txt | 231 ++++++++++++ > 2 files changed, 823 insertions(+) > create mode 100644 Documentation/arm64/acpi_object_usage.txt > create mode 100644 Documentation/arm64/why_use_acpi.txt > > diff --git a/Documentation/arm64/acpi_object_usage.txt b/Documentation/arm64/acpi_object_usage.txt > new file mode 100644 > index 0000000..2c4f733 > --- /dev/null > +++ b/Documentation/arm64/acpi_object_usage.txt > @@ -0,0 +1,592 @@ > +ACPI Tables > +----------- > +The expectations of individual ACPI tables are discussed in the list that > +follows. > + > +If a section number is used, it refers to a section number in the ACPI > +specification where the object is defined. If "Signature Reserved" is used, > +the table signature (the first four bytes of the table) is the only portion > +of the table recognized by the specification, and the actual table is defined > +outside of the UEFI Forum (see Section 5.2.6 of the specification). > + [snip....] > + > +ACPI Objects > +------------ > +The expectations on individual ACPI objects are discussed in the list that > +follows: > + > +Name Section Usage for ARMv8 Linux > +---- ------------ ------------------------------------------------- > +_ADR 6.1.1 Use as needed. [snip....] > + > +_DMA 6.2.4 Optional. > + > +_DSD 6.2.5 To be used with caution. If this object is used, try > + to use it within the constraints already defined by the > + Device Properties UUID. Only in rare circumstances > + should it be necessary to create a new _DSD UUID. > + > + In either case, submit the _DSD definition along with > + any driver patches for discussion, especially when > + device properties are used. A driver will not be > + considered complete without a corresponding _DSD > + description. Once approved by kernel maintainers, > + the UUID or device properties must then be registered > + with the UEFI Forum; this may cause some iteration as > + more than one OS will be registering entries. > + [snip...] So, this is my attempt to encapsulate what I think people want to have happen around the use of _DSD; I just want to make sure I point it out so it doesn't inadvertently get lost somehow. Is this far too little? Is it sufficient? If it only addresses part of the concerns, what did I miss? > + > +_OSC 6.2.11 This method can be a global method in ACPI (i.e., > + \_SB._OSC), or it may be associated with a specific > + device (e.g., \_SB.DEV0._OSC), or both. When used > + as a global method, only capabilities published in > + the ACPI specification are allowed. When used as > + a device-specifc method, the process described for > + using _DSD MUST be used to create an _OSC definition; > + out-of-process use of _OSC is not allowed. That is, > + submit the device-specific _OSC usage description as > + part of the kernel driver submission, get it approved > + by the kernel community, then register it with the > + UEFI Forum. Note that _OSC is very similar to _DSD in how it is defined in the ACPI spec. Hence, I suggest a very similar mechanism for vetting the use of _OSC in the kernel. Again: is this sufficient? > + > +\_OSI 5.7.2 Deprecated on ARM64. Any invocation of this method > + will print a warning on the console and return false. > + That is, as far as ACPI firmware is concerned, _OSI > + cannot be used to determine what sort of system is > + being used or what functionality is provided. The > + _OSC method is to be used instead. > + Just a side note that patches have been sent out to deprecate _OSI for arm64, and that a change request has been sent in to the ACPI spec committee to make it official (with an additional forewarning that _OSI will eventually be deprecated completely for all architectures). -- ciao, al ----------------------------------- Al Stone Software Engineer Linaro Enterprise Group al.stone@xxxxxxxxxx ----------------------------------- -- To unsubscribe from this list: send the line "unsubscribe linux-acpi" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
