linux-kernel - RE: [PATCH] ACPICA: make acpi_load

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Date:   Fri, 13 Sep 2019 14:20:21 +0000
From:   "Moore, Robert" <robert.moore@...el.com>
To:     Nikolaus Voss <nv@...n.de>
CC:     "Shevchenko, Andriy" <andriy.shevchenko@...el.com>,
        "Schmauss, Erik" <erik.schmauss@...el.com>,
        "Rafael J. Wysocki" <rjw@...ysocki.net>,
        Len Brown <lenb@...nel.org>,
        Jacek Anaszewski <jacek.anaszewski@...il.com>,
        "Pavel Machek" <pavel@....cz>, Dan Murphy <dmurphy@...com>,
        "linux-acpi@...r.kernel.org" <linux-acpi@...r.kernel.org>,
        "devel@...ica.org" <devel@...ica.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        Ferry Toth <ftoth@...fort.nl>,
        "nikolaus.voss@...wensteinmedical.de" 
        <nikolaus.voss@...wensteinmedical.de>
Subject: RE: [PATCH] ACPICA: make acpi_load_table() return table index



-----Original Message-----
From: Nikolaus Voss [mailto:nv@...n.de] 
Sent: Friday, September 13, 2019 12:44 AM
To: Moore, Robert <robert.moore@...el.com>
Cc: Shevchenko, Andriy <andriy.shevchenko@...el.com>; Schmauss, Erik <erik.schmauss@...el.com>; Rafael J. Wysocki <rjw@...ysocki.net>; Len Brown <lenb@...nel.org>; Jacek Anaszewski <jacek.anaszewski@...il.com>; Pavel Machek <pavel@....cz>; Dan Murphy <dmurphy@...com>; linux-acpi@...r.kernel.org; devel@...ica.org; linux-kernel@...r.kernel.org; Ferry Toth <ftoth@...fort.nl>; nikolaus.voss@...wensteinmedical.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