On Tue, Dec 08, 2009 at 03:03:30PM +0200, Artem Bityutskiy wrote: > On Mon, 2009-12-07 at 20:22 -0800, Dmitry Torokhov wrote: > > On Sun, Dec 06, 2009 at 09:47:04AM +0100, Pavel Machek wrote: > > > Hi! > > > > > > > > > > But runtime-pm.txt says for example: > > > > > > > > Generally, remote wake-up should be enabled for all input devices > > > > put into a low power state at run time. > > > > > > > > But in this case the requirement is to suppress input events from a > > > > given device, effectively muting and putting it into low power state, > > > > even though it's still open by some other parties. Runtime PM, on the > > > > other hand tries not to interfere with the normal usage of the device. > > > > > > > > Later: > > > > > > > > (3) ->runtime_idle() and ->runtime_suspend() can only be executed for a > > > > device the usage counter of which is equal to zero _and_ [...] > > > > > > > > which underlines the difference again: the usage counter (defined by > > > > common sense) won't be zero in our case, because the device is > > > > constantly kept open, while we want to mute it, putting it into a low > > > > power state. > > > ... > > > > Actually, this could be implemented by the various users cooperating in > > > > closing the device, letting it go to sleep automatically. But this > > > > requires strictly cooperating parties and is more complicated that > > > > flipping some master switch of the device. We're looking for this > > > > master switch, before needlessly building our own. > > > > > > Please just close the device properly. I do not think we want 100 > > > different 'please mute keys A and G', 'please mute middle mouse button', > > > ... interfaces anywhere near mainline. > > > > > > > I do not think it is practical to simply close the device, given that > > there may be several applications that have it open. I constantly see > > embedded guys adding custom knobs to the devices allowing them to shut > > off the device when not in use. Kind of runtame PM but user-initiated. > > > > I would really love to have it implemented in the driver core so the > > interface is the same for all drivers (that support this future). > > > > > Or just do it as local patch. > > > > I also see that gpio-keys is quite different in the sence that it can > > shut off buttons selectively. I fact, at the moment every button can be > > considered a separate device... But that would be too much overhead. > > > > They could probably split the keys into 2 groups (critical that should > > be always active) and not critical, that could be shut off, but I think > > they want teh flexibility of controlling this at runtime instead of > > doing it in board data. > > I suggested including this into the "abstract input device" model, but > you refuse this. But I still think it is a good idea. > > Indeed, if we look at an input device as at something abstract which has > many keys, why we cannot assume that separate keys can be > enabled/disabled? Just imagine you have a very advanced keybord :-) And > we simply implement an ioctl which enables/disables a specific key. The > generic layers just pass this ioctl down to the lower lever drivers. If > the specific input device or driver support it - fine, if not - it > returns -EINVAL or something like that. I refuse it because it will be supported by exactly 1 driver in the kernel - gpio-keys. It is the only driver that allows shut half of the "device" (because in reality it is a group of disjoint devices). It is the only case when "muting" a button means that IRQ is shut off abnd thus CPU can continue to sleep if that button is pressed. For all other devices that have 1 inettrupt per device, you still have to wake up, because you don't know whether the button that generated event is "important" or not. Now, there is a issue of waking up userspace task, additional scheduling and keeping CPU running longer than necessary for "uninteresting" keys. This can be solved by implementing a subscription model which allows filtering uninteresing events on a per-client basis at evdev level. This, if implemented properly, would work for _all_ input devices out there. You were not interested into looking into it (because for your particular and only device the otehr approach promises bigger savings) but I think we'll get there eventually. And the third topic - shutting (or putting into low power) entire device upon request from userspace. This again has much wider auditory than gpio-keys, or input devices layer for that matter. We may want to do so for other types of devices as well. That is why the question when to general PM list. -- Dmitry -- To unsubscribe from this list: send the line "unsubscribe linux-input" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
