> When the tty layer requests a serial break the usb_debug driver sends
> the magic packet. On the receiving side the magic packet is thrown
> away or a sysrq is activated depending on what kernel .config options
> have been set.
Really it ought to be runtime. And magic packets of data that can occur
in other places are asking for trouble in general paths.
> non usb uart based drivers implement the sysrq handling. This will
> allow other usb serial devices to implement sysrq handling as desired.
Which for the normal "break received" case is good
> + if (port->console) {
> + for (i = 0; i < urb->actual_length; i++, ch++) {
> + if (!usb_serial_handle_sysrq_char(port, *ch))
> + tty_insert_flip_char(tty, *ch, TTY_NORMAL);
> + }
> + tty_flip_buffer_push(tty);
> + } else if (urb->actual_length) {
> + i = tty_buffer_request_room(tty, urb->actual_length);
> + if (i) {
> + tty_insert_flip_string(tty, urb->transfer_buffer, i);
> tty_flip_buffer_push(tty);
I'd check urb->actual_length first ?
The bit that wants to be inline needs to look something
like
if (unlikely(port->sysrq_enabled))
uninlined_slow_path()
else {
tty_insert_flip_string(tty,
urb->transfer_buffer, i);
tty_flip_buffer_push(tty);
}
(You don't need the request_room and for non DMA block transfers its
probably actually not beneficial to override the default allocation
behaviour)
I suspect it would be a good thing to support both normal break and magic
packet as independant options (eg sysrq_enabled = 1 and = 2 or as
bitmasks, but with 0 = fastpath).
Alan
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