illumos gate

The usbkbm is streams driver and does push the (translated) key to stream with putnext() call. Since putnext() is commonly used method (it will reduce latency) to pass messages to next module in queue, this will end up with deep stack and in case of usbkbm, the whole chain is executing in interrupt context. In worst case this means we are drawing the console FB from interrupt context of usbkbm.

We would like to have interrupt routine done fast, so we should putq the message to our read queue and let STREAMS scheduler to handle the queue by calling usbkbm_rsrv().