linux-kernel - Re: [PATCH v2 16/28] ACPICA: Namespace: Add support of OSDT table.

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Message-ID: <558B0047.8050102@redhat.com>
Date:	Wed, 24 Jun 2015 13:08:55 -0600
From:	Al Stone <ahs3@...hat.com>
To:	Lv Zheng <lv.zheng@...el.com>,
	"Rafael J. Wysocki" <rafael.j.wysocki@...el.com>,
	Len Brown <len.brown@...el.com>
CC:	Lv Zheng <zetalog@...il.com>, linux-kernel@...r.kernel.org,
	linux-acpi@...r.kernel.org, Bob Moore <robert.moore@...el.com>
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@...el.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@...el.com>
> Signed-off-by: Bob Moore <robert.moore@...el.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@...hat.com
-----------------------------------
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