On Fri, Jul 11, 2014 at 09:28:47AM +0000, David Laight wrote: > From: Olivier Sobrie Olivier Sobrie > > Hi Alan and Davids, > > > > On Thu, Jul 10, 2014 at 04:50:03PM +0100, One Thousand Gnomes wrote: > > > On Thu, 10 Jul 2014 14:37:37 +0000 > > > David Laight <David.Laight@xxxxxxxxxx> wrote: > > > > > > > From: Olivier Sobrie > > > > ... > > > > > The function put_rxbuf_data() is called from the urb completion handler. > > > > > It puts the data of the urb transfer in the tty buffer with > > > > > tty_insert_flip_string_flags() and schedules a work queue in order to > > > > > push the data to the ldisc. > > > > > Problem is that we are in a urb completion handler so we can't wait > > > > > until there is room in the tty buffer. > > > > > > The tty provides the input queue, if the queue is full then just chuck > > > the data in the bitbucket. hso is trying to be far too clever. > > > > > > If hso is fast enough that the buffering isn't sufficient on the tty side > > > then we need to fix the tty buffer size. > > > > Ok I'll adapt the patch to drop the data that can't be put in the tty > > buffer. I test this and resend a new patch. > > If you are going to drop data, then ideally you want to discard entire ppp > packets. Depending on exactly how the interface works it might be that > urb are likely to contain complete packets. Indeed, urbs contains complete ppp packets. I see that the first and last byte are equal to 0x7e. > > So discarding entire urb might work better than discarding a few bytes. > (But don't even think of scanning the data stream in the usb driver - except > for experiments.) I will check with tty_buffer_request_room() that there is enough room to receive the frame before inserting the data in the tty buffer with tty_insert_flip_string(). -- Olivier -- To unsubscribe from this list: send the line "unsubscribe linux-usb" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
