On 08/08/16 14:51, Qing Huang wrote: > > > On 08/08/2016 01:44 PM, Frank Rowand wrote: >> On 07/29/16 22:39, Qing Huang wrote: >>> In normal condition, the device probe requests kept in deferred >>> queue would only be triggered for re-probing when another new device >>> probe is finished successfully. This change will set up a delayed >>> trigger work request if the current deferred probe being added is >>> the only one in the queue. This delayed work request will try to >>> reactivate any device from the deferred queue for re-probing later. >>> >>> By doing this, if the last device being probed in system boot process >>> has a deferred probe error, this particular device will still be able >>> to be probed again. >> I am trying to understand the use case. >> >> Can you explain the scenario you are trying to fix? If I understand >> correctly, you expect that something will change such that a later >> probe attempt will succeed. How will that change occur and why >> will the deferred probe list not be processed in this case? >> >> Why are you conditioning this on the deferred_probe_pending_list >> being empty? >> >> -Frank > > It turns out one corner case which we worried about has already been > solved in the really_probe() function by comparing > 'deferred_trigger_count' values. > > Another use case we are investigating now: when we probe a device, > the main thread returns EPROBE_DEFER from the driver after we spawn a > child thread to do the actual init work. So we can initialize > multiple similar devices at the same time. After the child thread > finishes its task, we can call driver_deferred_probe_trigger() > directly from child thread to re-probe the > device(driver_deferred_probe_trigger() has to be exported though). Or > we could rely on something in this patch to re-probe the deferred > devices from the pending list... > What do you suggest?
See commit 735a7ffb739b6efeaeb1e720306ba308eaaeb20e for how multi-threaded probes were intended to be handled. I don't know if this approach is used much or even usable, but that is the framework that was created. > Thanks, > -Qing < snip >