Re: proposal on runtime power management in hid

[Pavel Machek <pavel@suse.cz>]

Hi!

> > I think the simple and working solution would be never suspedning devices 
> > that have interface open through hidraw, unless user explicitly allows 
> > this through respective power/autosuspend setting in sysfs (which will by 
> > default be set to 'off' for HID devices anyway, right?).
> 
> That we already have. That's the simple copout. Do not enable autosuspend
> if you allow hidraw for a device. However, if normal users shall be able to use
> the hidraw device that means that autosuspend can never be enabled for the
> device, as we don't know when someone will use the device.
> 
> For hiddev we can do better, the device is not autosuspended while it is
> open. This allows allowing ordinary users to use the device. Doing so for
> hidraw would require to extended the low level hid API. But not as extensively
> as I suggested.
> 
> But I consider this to be a lost opportunity.
> Currently the ll driver must assume that the device is required to be fully
> operational when it is open. This means different things for ordinary input
> devices and "raw" devices. Raw devices must not be autosuspended when
> open at all. Ordinary devices must be able to process input.
> 
> But that is often overkill. In many situations, for example when a the screen
> saver is running, you only care that a key has been pressed, not which key.
> Drivers can save more power if they know this.


...way more power in some cases. Yes, I'd love to see interface like
that.

-- 
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