> -----Original Message----- > From: Jan Kiszka [mailto:jan.kiszka@xxxxxxxxxxx] > Sent: Monday, May 29, 2017 5:53 AM > To: Mika Westerberg <mika.westerberg@xxxxxxxxxxxxxxx> > Cc: Rafael J. Wysocki <rjw@xxxxxxxxxxxxx>; Len Brown <lenb@xxxxxxxxxx>; > Zheng, Lv <lv.zheng@xxxxxxxxx>; linux-acpi@xxxxxxxxxxxxxxx; Linux Kernel > Mailing List <linux-kernel@xxxxxxxxxxxxxxx>; devel@xxxxxxxxxx; Moore, > Robert <robert.moore@xxxxxxxxx> > 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@xxxxxxxxxxx> > >> --- > >> > >> 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. > [Moore, Robert] I'm not entirely sure what the table manager code looks like at this time, but ACPICA does in fact support table unloading. It is a rather dangerous thing to do, however -- unless you are careful about it. Basically, all handles that reference the table to be unloaded will go bad. > 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. > [Moore, Robert] I think that the maximum number of loaded ACPI tables is 255 at any given time. However, things are cleaned up after an unload such that repeated load/unload cycles should not consume resources. > Jan > > -- > Siemens AG, Corporate Technology, CT RDA ITP SES-DE Corporate Competence > Center Embedded Linux ��.n��������+%������w��{.n�����{�����ܨ}���Ơz�j:+v�����w����ޙ��&�)ߡ�a����z�ޗ���ݢj��w�f
