linux-kernel - Re: [PATCH] acpi: configfs: Unload SSDT on configfs entry removal

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Message-ID: <fff98a5c-e18f-d326-e5de-7401173d9af4@siemens.com>
Date:   Mon, 29 May 2017 14:53:11 +0200
From:   Jan Kiszka <jan.kiszka@...mens.com>
To:     Mika Westerberg <mika.westerberg@...ux.intel.com>
Cc:     "Rafael J. Wysocki" <rjw@...ysocki.net>,
        Len Brown <lenb@...nel.org>, Lv Zheng <lv.zheng@...el.com>,
        linux-acpi@...r.kernel.org,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        devel@...ica.org, Bob Moore <robert.moore@...el.com>
Subject: Re: [PATCH] acpi: configfs: Unload SSDT on configfs entry removal

On 2017-05-29 14:47, Mika Westerberg wrote:
> On Mon, May 29, 2017 at 01:33:29PM +0200, Jan Kiszka wrote:
>> Enhance acpi_load_table to also return the table index. Use that index
>> to unload the table again when the corresponding directory in configfs
>> gets removed. This allows to change SSDTs without rebooting the system.
>> It also allows to destroy devices again that a dynamically loaded SSDT
>> created.
>>
>> This is widely similar to the DT overlay behavior.
>>
>> Signed-off-by: Jan Kiszka <jan.kiszka@...mens.com>
>> ---
>>
>> Can someone explain to me why an unloaded table still sticks around in
>> sysfs and why we cannot release its ID and rather have to use a new one
>> when loading a modified version?
> 
> IIRC ACPICA relies the fact that SSDTs are never unloaded. Bob (CC'd)
> can correct me if I got it wrong.

OK... Is that standard-driven or just a limitation of this implementation?

Is there an upper limit of tables? I'm thinking of lengthy development
sessions that play with tables, loading and unloading modified versions.

Jan

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