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

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Message-ID: <20190913151228.GT2680@smile.fi.intel.com>
Date:   Fri, 13 Sep 2019 18:12:28 +0300
From:   "Shevchenko, Andriy" <andriy.shevchenko@...el.com>
To:     "Moore, Robert" <robert.moore@...el.com>
Cc:     Nikolaus Voss <nv@...n.de>,
        "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>,
        Jan Kiszka <jan.kiszka@...mens.com>
Subject: Re: [PATCH] ACPICA: make acpi_load_table() return table index

On Fri, Sep 13, 2019 at 05:20:21PM +0300, Moore, Robert wrote:
> -----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".

In Linux it became a part of ABI when the

commit 772bf1e2878ecfca0d1f332071c83e021dd9cf01
Author: Jan Kiszka <jan.kiszka@...mens.com>
Date:   Fri Jun 9 20:36:31 2017 +0200

    ACPI: configfs: Unload SSDT on configfs entry removal

appeared in the kernel.

> 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"));

-- 
With Best Regards,
Andy Shevchenko