Paul Walmsley <paul@xxxxxxxxx> writes: > Hello Kevin, > > On Tue, 17 Nov 2009, Kevin Hilman wrote: > >> Add use counters to omap_device to enable multiple potential users of >> an omap_device. This is needed if ever there are multiple users or >> multiple instances of a driver with a single omap_device. >> >> Without usecounting, with multiple users, the first one to call idle >> may forcibly idle the device while other users are still active. > > Could you please send along an example of the use case for this? The current use case is the serial driver (not yet ready for posting.) While there is only a single driver bound to the omap_device, there are effectivily multiple instances of the driver. One for initial init/probe requriring and early _enable, followed by _idle in the late_init hook. Another when the actual serial driver gets started and the inactivity timers etc. start firing. These usages overlap slightly and the easiest way I saw to handle this was with usecounting. > I would prefer not to add usecounting at this layer unless it is > absolutely necessary, since only one driver should be bound to a > device at a time. What about mulitple instances of the same driver? Or, what about drivers like i2c which might do _enable/_idle on a per-transfer basis and there might be multiple transfers pending at any given time. We already have use-counting in the clock framework for this same purpose. I'm essentially proposing the usecounting for the same reason, but it also need to protect enable/idle parts of hwmod as well. Maybe usecounting at the hwmod level is more appropriate since that's where the problem lies. I'm fine with that. Kevin -- 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
