RE: [PATCH v2 16/28] ACPICA: Namespace: Add support of OSDT table.

Moore, Robert
2015-06-24T20:02:25Z

It is the current plan to add this to the next revision of the ACPI specification.

In the meantime, the OSDT looks exactly like a DSDT or SSDT (hence the "SDT" suffix), with the only difference being the signature "OSDT":

DefinitionBlock ("osdt.aml", "OSDT", 2, "Intel", "Template", 0x00000001)
{

The current iASL compiler will emit a template for you if you want:

iasl -T OSDT

We are working on the proposal/ECR for the ACPI spec.
Bob

> -----Original Message-----
> From: Al Stone [mailto:ahs3@redhat.com]
> Sent: Wednesday, June 24, 2015 12:09 PM
> To: Zheng, Lv; Wysocki, Rafael J; Brown, Len
> Cc: Lv Zheng; linux-kernel@vger.kernel.org; linux-acpi@vger.kernel.org;
> Moore, Robert
> Subject: Re: [PATCH v2 16/28] ACPICA: Namespace: Add support of OSDT
> table.
>
> On 06/23/2015 09:04 PM, Lv Zheng wrote:
> > From: Bob Moore <robert.moore@intel.com>
> >
> > ACPICA commit 27415c82fcecf467446f66d1007a0691cc5f3709
> >
> > This patch adds OSDT (Override System Definition Table) support.
> > When OSDT is loaded, conflict namespace objects will be overridden by
> > the AML interpreter. Bob Moore, Lv Zheng.
> >
> > Link: https://github.com/acpica/acpica/commit/27415c82
> > Signed-off-by: Lv Zheng <lv.zheng@intel.com>
> > Signed-off-by: Bob Moore <robert.moore@intel.com>
> > ---
> > drivers/acpi/acpica/nsparse.c | 7 +++++++
> > drivers/acpi/acpica/tbxfload.c | 6 +++++-
> > drivers/acpi/acpica/utmisc.c | 3 ++-
> > include/acpi/actbl.h | 1 +
> > 4 files changed, 15 insertions(+), 2 deletions(-)
> >
> > diff --git a/drivers/acpi/acpica/nsparse.c
> > b/drivers/acpi/acpica/nsparse.c index c95a119..57a4cfe 100644
> > --- a/drivers/acpi/acpica/nsparse.c
> > +++ b/drivers/acpi/acpica/nsparse.c
> > @@ -117,6 +117,13 @@ acpi_ns_one_complete_parse(u32 pass_number,
> > (u8) pass_number);
> > }
> >
> > + /* Found OSDT table, enable the namespace override feature */
> > +
> > + if (ACPI_COMPARE_NAME(table->signature, ACPI_SIG_OSDT) &&
> > + pass_number == ACPI_IMODE_LOAD_PASS1) {
> > + walk_state->namespace_override = TRUE;
> > + }
> > +
> > if (ACPI_FAILURE(status)) {
> > acpi_ds_delete_walk_state(walk_state);
> > goto cleanup;
> > diff --git a/drivers/acpi/acpica/tbxfload.c
> > b/drivers/acpi/acpica/tbxfload.c index b63e35d..960bd99 100644
> > --- a/drivers/acpi/acpica/tbxfload.c
> > +++ b/drivers/acpi/acpica/tbxfload.c
> > @@ -173,7 +173,11 @@ static acpi_status acpi_tb_load_namespace(void)
> > &&
> > !ACPI_COMPARE_NAME(&
> > (acpi_gbl_root_table_list.tables[i].
> > - signature), ACPI_SIG_PSDT))
> > + signature), ACPI_SIG_PSDT)
> > + &&
> > + !ACPI_COMPARE_NAME(&
> > + (acpi_gbl_root_table_list.tables[i].
> > + signature), ACPI_SIG_OSDT))
> > ||
> > ACPI_FAILURE(acpi_tb_validate_table
> > (&acpi_gbl_root_table_list.tables[i]))) { diff --
> git
> > a/drivers/acpi/acpica/utmisc.c b/drivers/acpi/acpica/utmisc.c index
> > cbb7034..28099e2 100644
> > --- a/drivers/acpi/acpica/utmisc.c
> > +++ b/drivers/acpi/acpica/utmisc.c
> > @@ -97,7 +97,8 @@ u8 acpi_ut_is_aml_table(struct acpi_table_header
> > *table)
> >
> > if (ACPI_COMPARE_NAME(table->signature, ACPI_SIG_DSDT) ||
> > ACPI_COMPARE_NAME(table->signature, ACPI_SIG_PSDT) ||
> > - ACPI_COMPARE_NAME(table->signature, ACPI_SIG_SSDT)) {
> > + ACPI_COMPARE_NAME(table->signature, ACPI_SIG_SSDT) ||
> > + ACPI_COMPARE_NAME(table->signature, ACPI_SIG_OSDT)) {
> > return (TRUE);
> > }
> >
> > diff --git a/include/acpi/actbl.h b/include/acpi/actbl.h index
> > cb8a6b9..2d5faf5 100644
> > --- a/include/acpi/actbl.h
> > +++ b/include/acpi/actbl.h
> > @@ -65,6 +65,7 @@
> > #define ACPI_SIG_DSDT "DSDT" /* Differentiated System
> Description Table */
> > #define ACPI_SIG_FADT "FACP" /* Fixed ACPI Description Table
> */
> > #define ACPI_SIG_FACS "FACS" /* Firmware ACPI Control
> Structure */
> > +#define ACPI_SIG_OSDT "OSDT" /* Override System Description
> Table */
> > #define ACPI_SIG_PSDT "PSDT" /* Persistent System Description
> Table */
> > #define ACPI_SIG_RSDP "RSD PTR " /* Root System Description
> Pointer */
> > #define ACPI_SIG_RSDT "RSDT" /* Root System Description Table
> */
> >
>
> I'm a little puzzled by this patch and the previous one (15-16/28). I see
> no definition for OSDT in the ACPI spec nor at http://uefi.org/acpi.
> Personally, I like the feature, but I really don't like the idea that I'm
> now going to have to go dig around to figure out what this table looks
> like and what its semantics are supposed to be. Without doing that,
> though, it is impossible for me to tell if these patches are doing the
> right thing.
>
> So, can I get a URL to the OSDT definition? And if this is going to be
> part of ACPI, please submit it as a change request to the spec; I sit on
> the committee but this table hasn't come up at all to date (I just
> searched the issue data base a few minutes ago to make sure I hadn't
> missed it somewhere). If OSDT is not going to be part of standard ACPI,
> why the divergence from the spec?
>
> --
> ciao,
> al
> -----------------------------------
> Al Stone
> Software Engineer
> Red Hat, Inc.
> ahs3@redhat.com
> -----------------------------------