linux-kernel - Re: [RFC PATCH 1/5] ACPI: Add acpi_lookup

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Date:	Fri, 31 Aug 2012 10:24:12 -0600
From:	Toshi Kani <toshi.kani@...com>
To:	Bjorn Helgaas <bhelgaas@...gle.com>
Cc:	linux-acpi@...r.kernel.org, linux-kernel@...r.kernel.org,
	lenb@...nel.org, liuj97@...il.com, isimatu.yasuaki@...fujitsu.com
Subject: Re: [RFC PATCH 1/5] ACPI: Add acpi_lookup_driver() function

On Thu, 2012-08-30 at 22:42 -0700, Bjorn Helgaas wrote:
> On Thu, Aug 30, 2012 at 1:16 PM, Toshi Kani <toshi.kani@...com> wrote:
> > Added acpi_lookup_driver(), which looks up an associated driver
> > for the notified ACPI device object by walking through the list
> > of ACPI drivers.
> >
> > Signed-off-by: Toshi Kani <toshi.kani@...com>
> > ---
> >  drivers/acpi/scan.c     |   65 +++++++++++++++++++++++++++++++++++++++++++++++
> >  include/acpi/acpi_bus.h |    2 +
> >  2 files changed, 67 insertions(+), 0 deletions(-)
> >
> > diff --git a/drivers/acpi/scan.c b/drivers/acpi/scan.c
> > index d1ecca2..d0e0d18 100644
> > --- a/drivers/acpi/scan.c
> > +++ b/drivers/acpi/scan.c
> > @@ -1630,3 +1630,68 @@ int __init acpi_scan_init(void)
> >
> >         return result;
> >  }
> > +
> > +static int acpi_match_driver(struct device_driver *drv, void *data)
> > +{
> > +       struct acpi_driver *driver = to_acpi_driver(drv);
> > +       struct acpi_device *device = (struct acpi_device *) data;
> > +       int ret;
> > +
> > +       ret = acpi_match_device_ids(device, driver->ids);
> > +       if (!ret)
> > +               device->driver = driver;
> > +
> > +       return !ret;
> > +}
> > +
> > +/**
> > + * acpi_lookup_driver: Look up a driver for the notified ACPI device
> > + * @handle: ACPI handle of the notified device object
> > + * @event: Notify event
> > + *
> > + * Look up an associated driver for the notified ACPI device object
> > + * by walking through the list of ACPI drivers.
> > + */
> > +struct acpi_driver *acpi_lookup_driver(acpi_handle handle, u32 event)
> > +{
> > +       struct acpi_device *device;
> > +       struct acpi_driver *driver = NULL;
> > +       unsigned long long sta;
> > +       int type;
> > +       int ret;
> > +
> > +       /* allocate a temporary device object */
> > +       device = kzalloc(sizeof(struct acpi_device), GFP_KERNEL);
> > +       if (!device) {
> > +               pr_err(PREFIX "No memory to allocate a tmp device\n");
> > +               return NULL;
> > +       }
> > +
> > +       ret = acpi_bus_type_and_status(handle, &type, &sta);
> > +       if (ret) {
> > +               pr_err(PREFIX "Failed to get type of device\n");
> > +               goto out;
> > +       }
> > +
> > +       /* setup this temporary device object */
> > +       INIT_LIST_HEAD(&device->pnp.ids);
> > +       device->device_type = type;
> > +       device->handle = handle;
> > +       device->parent = acpi_bus_get_parent(handle);
> > +       device->dev.bus = &acpi_bus_type;
> > +       device->driver = NULL;
> > +       STRUCT_TO_INT(device->status) = sta;
> > +       device->status.present = 1;
> > +
> > +       /* set HID to this device object */
> > +       acpi_device_set_id(device);
> > +
> > +       /* lookup a matching driver */
> > +       (void) bus_for_each_drv(device->dev.bus, NULL,
> > +                                       device, acpi_match_driver);
> > +       driver = device->driver;
> 
> This path is used when we receive a Notify to a device and a matching
> driver has been registered, but the driver is not bound to the device.
>  For example, it may be a newly-added device where we haven't bound a
> driver to it yet.
> 
> Is there anything that prevents us from unloading the driver between
> here (the point where we capture the "struct acpi_driver *") and the
> point where we call "driver->ops.sys_notify"?

Hi Bjorn,

That's a very good question.  I will look into how we protect a driver
from unloading when we try to attach & probe a driver in the
acpi_add_single_object() path, and see if we can use a similar way to
protect it here as well.

Thanks,
-Toshi


> > +
> > +out:
> > +       kfree(device);
> > +       return driver;
> > +}
> > diff --git a/include/acpi/acpi_bus.h b/include/acpi/acpi_bus.h
> > index bde976e..a773b46 100644
> > --- a/include/acpi/acpi_bus.h
> > +++ b/include/acpi/acpi_bus.h
> > @@ -345,6 +345,8 @@ extern int unregister_acpi_notifier(struct notifier_block *);
> >
> >  extern int register_acpi_bus_notifier(struct notifier_block *nb);
> >  extern void unregister_acpi_bus_notifier(struct notifier_block *nb);
> > +extern struct acpi_driver *acpi_lookup_driver(acpi_handle handle, u32 event);
> > +
> >  /*
> >   * External Functions
> >   */
> > --
> > 1.7.7.6
> >


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