RE: [PATCH] ACPICA: make acpi_load_table() return table index

[Moore, Robert]

-----Original Message-----
From: Nikolaus Voss [mailto:nv@xxxxxxx] 
Sent: Friday, September 13, 2019 12:44 AM
To: Moore, Robert <robert.moore@xxxxxxxxx>
Cc: Shevchenko, Andriy <andriy.shevchenko@xxxxxxxxx>; Schmauss, Erik <erik.schmauss@xxxxxxxxx>; Rafael J. Wysocki <rjw@xxxxxxxxxxxxx>; Len Brown <lenb@xxxxxxxxxx>; Jacek Anaszewski <jacek.anaszewski@xxxxxxxxx>; Pavel Machek <pavel@xxxxxx>; Dan Murphy <dmurphy@xxxxxx>; linux-acpi@xxxxxxxxxxxxxxx; devel@xxxxxxxxxx; linux-kernel@xxxxxxxxxxxxxxx; Ferry Toth <ftoth@xxxxxxxxxx>; nikolaus.voss@xxxxxxxxxxxxxxxxxxxxx
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