On Thu, 30 Jun 2011, Kevin Hilman wrote: > I'm still confused about the usage_count increment around ->probe > though. As a few people have already pointed out, some subsystems do perform runtime PM on driverless devices. The basic idea is simple: We don't want any PM callbacks to race with each other or with other driver-core callbacks. Incrementing the usage_count prevents runtime_suspend callbacks while the probe callback is running. This does leave open the possibility of runtime_resume occurring concurrently with probe. For the most part this should be okay because without a driver, no part of the kernel will try to resume the device. Hmmm, but a resume could occur as a result of userspace writing to a sysfs attribute. It looks like we need to add some lock_device() calls to control_store() and autosuspend_delay_ms_store(). Alan Stern -- To unsubscribe from this list: send the line "unsubscribe linux-omap" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
