I'm currently working on a project where I'd like to have an omap board
running linux be a usb-to-uart converter (using f_acm). I have an
application that holds both the ttyGS* and the ttyO* port (the physical
uart port) open, polls for readable data, and writes any incoming data
to the other side.
I'd also like the host to be able to configure baudrate, parity, etc.
My thought on how to achieve this is to modify how the ttyGS* ports
behave by adding a POLLPRI event when set_line_coding is received. In
order to do that several steps will have to be taken:
- one of:
1. add a poll() callback to struct tty_operations and call it in
n_tty_poll(). u_serial and f_acm will implement required
callbacks to allow returning POLLPRI when necessary.
2. add a flag to struct tty_struct that indicates an exceptional
condition and make n_tty_poll() return POLLPRI if that flag is
set. this will also require a new wait queue to allow us to wait
for such an event.
- after receiving SET_LINE_CODING (and verifying it), set whatever flag
is necessary to wake the user with POLLPRI.
- implement the ioctl() callback in u_serial and f_acm to allow the
user to get the line coding set by the host, with which it can
configure the hardware port accordingly.
Does my approach make sense? Assuming I do that, which tree should such
a series be sent to? usb-gadget? tty?
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