On Wed, Jun 14, 2017 at 11:20 AM, Tal Shorer <tal.shorer@xxxxxxxxx> wrote: > On Wed, Jun 14, 2017 at 4:15 AM, Alan Cox <gnomes@xxxxxxxxxxxxxxxxxxx> wrote: >> On Tue, 13 Jun 2017 09:52:07 +0300 >> Tal Shorer <tal.shorer@xxxxxxxxx> wrote: >> >>> If a tty driver wants to notify the user of some exceptional event, >>> such as a usb cdc acm device set_line_coding event, it needs a way to >>> modify the mask returned by poll() and possible also add wait queues. >>> In order to do that, we allow the driver to supply a poll() callback >>> of its own, which will be called in n_tty_poll(). >>> >>> Signed-off-by: Tal Shorer <tal.shorer@xxxxxxxxx> >> >> You might be in any line discipline so you need to support that for each >> ldisc that supports poll(). Also what do I do when I get an exception >> event - what does it mean, how do I understand that, are you proposing a >> standardized meaning ? Have you checked whether that conflicts with SuS >> v3 or POSIX ? What will it do with existing code. >> >> At the very least it probably has to be something you turn on, and you >> might then want to model it on the pty/tty interface logic and extend >> TIOCPKT a shade. > That would cut it, but TIOCPKT is too coupled with having a linked tty. > I could make acm behave like a pty (accept TIOCPKT and issue the > ctrl_status bits), but for that I need n_tty to know that packet does > not always mean a linked tty is present, and that in case it isn't we > take our own ctrl_status bits instead of the link's. I could write a > small (inline?) function to fetch the correct ctrl_status bits and put > that in n_tty. Does that make sense? Or (maybe) better yet, I can do a hack and have the acm tty point to itself as the link, which means n_tty doesn't have to change at all. Any thoughts? -- 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
