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drivercore: Add driver probe deferral mechanism
Allow drivers to report at probe time that they cannot get all the resources required by the device, and should be retried at a later time. This should completely solve the problem of getting devices initialized in the right order. Right now this is mostly handled by mucking about with initcall ordering which is a complete hack, and doesn't even remotely handle the case where device drivers are in modules. This approach completely sidesteps the issues by allowing driver registration to occur in any order, and any driver can request to be retried after a few more other drivers get probed. v4: - Integrate Manjunath's addition of a separate workqueue - Change -EAGAIN to -EPROBE_DEFER for drivers to trigger deferral - Update comment blocks to reflect how the code really works v3: - Hold off workqueue scheduling until late_initcall so that the bulk of driver probes are complete before we start retrying deferred devices. - Tested with simple use cases. Still needs more testing though. Using it to get rid of the gpio early_initcall madness, or to replace the ASoC internal probe deferral code would be ideal. v2: - added locking so it should no longer be utterly broken in that regard - remove device from deferred list at device_del time. - Still completely untested with any real use case, but has been boot tested. Signed-off-by: Grant Likely <[email protected]> Cc: Mark Brown <[email protected]> Cc: Arnd Bergmann <[email protected]> Cc: Dilan Lee <[email protected]> Cc: Manjunath GKondaiah <[email protected]> Cc: Alan Stern <[email protected]> Cc: Tony Lindgren <[email protected]> Cc: Alan Cox <[email protected]> Reviewed-by: Mark Brown <[email protected]> Acked-by: David Daney <[email protected]> Reviewed-by: Arnd Bergmann <[email protected]> Signed-off-by: Greg Kroah-Hartman <[email protected]>
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