On Monday, September 21, 2015 04:02:41 PM Tomeu Vizoso wrote:
> Lets implementations of the match() callback in struct bus_type to
> return errors and if it's -EPROBE_DEFER then queue the device for
> deferred probing.
>
> This is useful to buses such as AMBA in which devices are registered
> before their matching information can be retrieved from the HW
> (typically because a clock driver hasn't probed yet).
>
> Signed-off-by: Tomeu Vizoso <tomeu.vizoso@xxxxxxxxxxxxx>
> ---
>
>
> drivers/base/dd.c | 24 ++++++++++++++++++++++--
> include/linux/device.h | 2 +-
> 2 files changed, 23 insertions(+), 3 deletions(-)
>
> diff --git a/drivers/base/dd.c b/drivers/base/dd.c
> index be0eb4639128..7dc04ee81c8b 100644
> --- a/drivers/base/dd.c
> +++ b/drivers/base/dd.c
> @@ -488,6 +488,7 @@ static int __device_attach_driver(struct device_driver *drv, void *_data)
> struct device_attach_data *data = _data;
> struct device *dev = data->dev;
> bool async_allowed;
> + int ret;
>
> /*
> * Check if device has already been claimed. This may
> @@ -498,8 +499,17 @@ static int __device_attach_driver(struct device_driver *drv, void *_data)
> if (dev->driver)
> return -EBUSY;
>
> - if (!driver_match_device(drv, dev))
> + ret = driver_match_device(drv, dev);
> + if (!ret)
> return 0;
> + else if (ret < 0) {
> + if (ret == -EPROBE_DEFER) {
> + dev_dbg(dev, "Device match requests probe deferral\n");
> + driver_deferred_probe_add(dev);
> + } else
> + dev_warn(dev, "Bus failed to match device: %d", ret);
> + return ret;
> + }
The code below was reachable if an error was returned from driver_match_device()
before this patch. What's the reason for changing that?
Shouldn't the code here really be:
ret = driver_match_device(drv, dev);
if (!ret)
return 0;
if (ret == -EPROBE_DEFER) {
driver_deferred_probe_add(dev);
return ret;
}
> async_allowed = driver_allows_async_probing(drv);
>
> @@ -619,6 +629,7 @@ void device_initial_probe(struct device *dev)
> static int __driver_attach(struct device *dev, void *data)
> {
> struct device_driver *drv = data;
> + int ret;
>
> /*
> * Lock device and try to bind to it. We drop the error
> @@ -630,8 +641,17 @@ static int __driver_attach(struct device *dev, void *data)
> * is an error.
> */
>
> - if (!driver_match_device(drv, dev))
> + ret = driver_match_device(drv, dev);
> + if (!ret)
> + return 0;
> + else if (ret < 0) {
> + if (ret == -EPROBE_DEFER) {
> + dev_dbg(dev, "Device match requests probe deferral\n");
> + driver_deferred_probe_add(dev);
> + } else
> + dev_warn(dev, "Bus failed to match device: %d", ret);
> return 0;
Same comment here, plus why do we return 0 at this point?
> + }
>
> if (dev->parent) /* Needed for USB */
> device_lock(dev->parent);
> diff --git a/include/linux/device.h b/include/linux/device.h
> index 5d7bc6349930..8e7b806f0744 100644
> --- a/include/linux/device.h
> +++ b/include/linux/device.h
> @@ -70,7 +70,7 @@ extern void bus_remove_file(struct bus_type *, struct bus_attribute *);
> * @dev_groups: Default attributes of the devices on the bus.
> * @drv_groups: Default attributes of the device drivers on the bus.
> * @match: Called, perhaps multiple times, whenever a new device or driver
> - * is added for this bus. It should return a nonzero value if the
> + * is added for this bus. It should return a positive value if the
> * given device can be handled by the given driver.
> * @uevent: Called when a device is added, removed, or a few other things
> * that generate uevents to add the environment variables.
>
Thanks,
Rafael
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