linux-kernel - Re: [PATCH] ACPI / scan: Follow priorities of IDs when matching scan handlers

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Date:	Sun, 03 Feb 2013 14:05:42 +0100
From:	"Rafael J. Wysocki" <rjw@...k.pl>
To:	Yinghai Lu <yinghai@...nel.org>
Cc:	Toshi Kani <toshi.kani@...com>,
	ACPI Devel Maling List <linux-acpi@...r.kernel.org>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	Bjorn Helgaas <bhelgaas@...gle.com>,
	Mika Westerberg <mika.westerberg@...ux.intel.com>,
	Matthew Garrett <matthew.garrett@...ula.com>,
	Jiang Liu <liuj97@...il.com>,
	LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] ACPI / scan: Follow priorities of IDs when matching scan handlers

On Saturday, February 02, 2013 08:54:46 PM Yinghai Lu wrote:
> On Sat, Feb 2, 2013 at 4:52 PM, Rafael J. Wysocki <rjw@...k.pl> wrote:
> > From: Rafael J. Wysocki <rafael.j.wysocki@...el.com>
> >
> > The IDs of ACPI device nodes stored in their pnp.ids member arrays
> > are sorted by decreasing priority (i.e. the highest-priority ID is
> > the first entry).  This means that when matching scan handlers to
> > device nodes, the namespace scanning code should walk the list of
> > scan handlers for each device node ID instead of walking the list
> > of device node IDs for each handler (the latter causes the first
> > handler matching any of the device node IDs to be chosen, although
> > there may be another handler matching an ID of a higher priority
> > which should be preferred).  Make the code follow this observation.
> >
> > This change has been suggested and justified by Toshi Kani.
> >
> > Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@...el.com>
> > ---
> >  drivers/acpi/scan.c |   42 +++++++++++++++++++++++++++++-------------
> >  1 file changed, 29 insertions(+), 13 deletions(-)
> >
> > Index: test/drivers/acpi/scan.c
> > ===================================================================
> > --- test.orig/drivers/acpi/scan.c
> > +++ test/drivers/acpi/scan.c
> > @@ -1556,26 +1556,42 @@ static acpi_status acpi_bus_check_add(ac
> >         return AE_OK;
> >  }
> >
> > -static int acpi_scan_attach_handler(struct acpi_device *device)
> > +static int acpi_scan_do_attach_handler(struct acpi_device *device, char *id)
> >  {
> >         struct acpi_scan_handler *handler;
> > -       int ret = 0;
> >
> >         list_for_each_entry(handler, &acpi_scan_handlers_list, list_node) {
> > -               const struct acpi_device_id *id;
> > +               const struct acpi_device_id *devid;
> >
> > -               id = __acpi_match_device(device, handler->ids);
> > -               if (!id)
> > -                       continue;
> > -
> > -               ret = handler->attach(device, id);
> > -               if (ret > 0) {
> > -                       device->handler = handler;
> > -                       break;
> > -               } else if (ret < 0) {
> > -                       break;
> > +               for (devid = handler->ids; devid->id[0]; devid++) {
> > +                       int ret;
> > +
> > +                       if (strcmp((char *)devid->id, id))
> > +                               continue;
> > +
> > +                       ret = handler->attach(device, devid);
> > +                       if (ret > 0) {
> > +                               device->handler = handler;
> > +                               return ret;
> > +                       } else if (ret < 0) {
> > +                               return ret;
> > +                       }
> >                 }
> >         }
> > +       return 0;
> > +}
> > +
> > +static int acpi_scan_attach_handler(struct acpi_device *device)
> > +{
> > +       struct acpi_hardware_id *hwid;
> > +       int ret = 0;
> > +
> > +       list_for_each_entry(hwid, &device->pnp.ids, list) {
> > +               ret = acpi_scan_do_attach_handler(device, hwid->id);
> > +               if (ret)
> > +                       break;
> > +
> > +       }
> >         return ret;
> >  }
> >
> >
> 
> Looks like right to honor the order in pnp.ids.
> 
> so there is same problem with acpi_bus_match/acpi_match_device_ids
> that need to fixed?

Yes, there is the same problem, but I'm not sure we can actually fix it.

The driver core walks the list of available drivers for the given bus just
once in bus_probe_device(), so it cannot check all drivers against each of
the given device IDs.  So it looks like acpi_bus_match() does all it can do
(one more reason to get rid of the ACPI bus type IMHO).

Thanks,
Rafael


-- 
I speak only for myself.
Rafael J. Wysocki, Intel Open Source Technology Center.
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