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Add documentation on meaning of -EPROBE_DEFER

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Add a bit of documentation on what it means when a driver .probe() hook
returns the -EPROBE_DEFER error code, including the limitation that
-EPROBE_DEFER should be returned as early as possible, before the driver
starts to register child devices.

Also: minor markup fixes in the same file

Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: Saravana Kannan <saravanak@google.com>
Cc: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Reviewed-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Signed-off-by: Grant Likely <grant.likely@arm.com>
Link: https://lore.kernel.org/r/20200327170132.17275-1-grant.likely@arm.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Grant Likely 2020-03-27 17:01:32 +00:00 committed by Greg Kroah-Hartman
parent 45bb08de65
commit fbc35b45f9
1 changed files with 27 additions and 5 deletions
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32
Documentation/driver-api/driver-model/driver.rst
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@ -4,7 +4,6 @@ Device Drivers
See the kerneldoc for the struct device_driver.
Allocation
~~~~~~~~~~
@ -167,9 +166,26 @@ the driver to that device.
A driver's probe() may return a negative errno value to indicate that
the driver did not bind to this device, in which case it should have
released all resources it allocated::
released all resources it allocated.
void (*sync_state)(struct device *dev);
Optionally, probe() may return -EPROBE_DEFER if the driver depends on
resources that are not yet available (e.g., supplied by a driver that
hasn't initialized yet). The driver core will put the device onto the
deferred probe list and will try to call it again later. If a driver
must defer, it should return -EPROBE_DEFER as early as possible to
reduce the amount of time spent on setup work that will need to be
unwound and reexecuted at a later time.
.. warning::
-EPROBE_DEFER must not be returned if probe() has already created
child devices, even if those child devices are removed again
in a cleanup path. If -EPROBE_DEFER is returned after a child
device has been registered, it may result in an infinite loop of
.probe() calls to the same driver.
::
void (*sync_state) (struct device *dev);
sync_state is called only once for a device. It's called when all the consumer
devices of the device have successfully probed. The list of consumers of the
@ -212,6 +228,8 @@ over management of devices from the bootloader, the usage of sync_state() is
not restricted to that. Use it whenever it makes sense to take an action after
all the consumers of a device have probed::
::
int (*remove) (struct device *dev);
remove is called to unbind a driver from a device. This may be
@ -224,11 +242,15 @@ not. It should free any resources allocated specifically for the
device; i.e. anything in the device's driver_data field.
If the device is still present, it should quiesce the device and place
it into a supported low-power state::
it into a supported low-power state.
::
int (*suspend) (struct device *dev, pm_message_t state);
suspend is called to put the device in a low power state::
suspend is called to put the device in a low power state.
::
int (*resume) (struct device *dev);