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

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Date:	Thu, 30 Aug 2012 22:42:37 -0700
From:	Bjorn Helgaas <bhelgaas@...gle.com>
To:	Toshi Kani <toshi.kani@...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, 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"?

> +
> +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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