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SubjectRE: [PATCH] ACPICA: make acpi_load_table() return table index
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-----Original Message-----
From: Nikolaus Voss [mailto:nv@vosn.de]
Sent: Friday, September 13, 2019 12:44 AM
To: Moore, Robert <robert.moore@intel.com>
Cc: Shevchenko, Andriy <andriy.shevchenko@intel.com>; Schmauss, Erik <erik.schmauss@intel.com>; Rafael J. Wysocki <rjw@rjwysocki.net>; Len Brown <lenb@kernel.org>; Jacek Anaszewski <jacek.anaszewski@gmail.com>; Pavel Machek <pavel@ucw.cz>; Dan Murphy <dmurphy@ti.com>; linux-acpi@vger.kernel.org; devel@acpica.org; linux-kernel@vger.kernel.org; Ferry Toth <ftoth@telfort.nl>; nikolaus.voss@loewensteinmedical.de
Subject: RE: [PATCH] ACPICA: make acpi_load_table() return table index

Bob,

On Thu, 12 Sep 2019, Moore, Robert wrote:
> The ability to unload an ACPI table (especially AML tables such as
> SSDTs) is in the process of being deprecated in ACPICA -- since it is
> also deprecated in the current ACPI specification. This is being done
> because of the difficulty of deleting the namespace entries for the
> table. FYI, Windows does not properly support this function either.

ok, I see it can be a problem to unload an AML table with all it's consequences e.g. with respect to driver unregistering in setups with complex dependencies. It will only work properly under certain conditions
- nevertheless acpi_tb_unload_table() is still exported in ACPICA and we should get this working as it worked before.

AcpiTbUnloadTable is not exported, it is an internal interface only -- as recognized by the "AcpiTb". I'm not sure that I want to change the interface to AcpiLoadTable just for something that is being deprecated. Already, we throw an ACPI_EXCEPTION if the Unload operator is encountered in the AML byte stream. The same thing with AcpiUnloadParentTable - it is being deprecated.


ACPI_EXCEPTION ((AE_INFO, AE_NOT_IMPLEMENTED,
"AML Unload operator is not supported"));


The API change I request is not directly related to table unloading, it's just that the index of the loaded table is returned for future reference:

[...]

>> diff --git a/include/acpi/acpixf.h b/include/acpi/acpixf.h index
>> 3845c8fcc94e5..c90bbdc4146a6 100644
>> --- a/include/acpi/acpixf.h
>> +++ b/include/acpi/acpixf.h
>> @@ -452,7 +452,8 @@ ACPI_EXTERNAL_RETURN_STATUS(acpi_status ACPI_INIT_FUNCTION
>> u8 physical))
>>
>> ACPI_EXTERNAL_RETURN_STATUS(acpi_status
>> - acpi_load_table(struct acpi_table_header *table))
>> + acpi_load_table(struct acpi_table_header *table,
>> + u32 *table_idx))
>>
>> ACPI_EXTERNAL_RETURN_STATUS(acpi_status
>> acpi_unload_parent_table(acpi_handle object))
>> --
>> 2.17.1
>>

This allows for a simple fix of the regression and doesn't imply future support for table unloading. Would this be acceptable?

Niko

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