Re: USB output in ucom

On Fri, Jul 11, 2025 at 06:20:50AM +0000, Emmanuel Dreyfus wrote:
> Hello
> 
> I am still working on ucom console. My first cn_putc used ucomwrite(), 
> but it always hung after reaching multi-user. I suspect a locking problem.
> 
> Another approach is to use USB transfers directly, bypassing a lot of
> code in ucom.c, tty.c and tty_subr.c. I try this:
> 
>   error = usbd_create_xfer(sc->sc_bulkout_pipe,
>       sc->sc_obufsize, USBD_SYNCHRONOUS, 0,
>       &ucomcons_xfer_out);
>   
>   u_char *data = usbd_get_buffer(ucomcons_xfer_out;
>   u_char *buf = __UNCONST("hello world!\nxxx\n");
>   int cnt = 13;;
>   
>   if (sc->sc_methods->ucom_write != NULL)
>           sc->sc_methods->ucom_write(sc->sc_parent, sc->sc_portno,
>               data, buf, &cnt);
>   else
>           memcpy(data, buf, cnt);
>   
>   usbd_setup_xfer(ucomcons_xfer_out, sc, data, cnt,
>       0, USBD_NO_TIMEOUT, NULL /* no cb */);
>   
>   usbd_transfer(ucomcons_xfer_out);
> 
> This actually output "ollow world!" on the serial line. How does the
> "he" turns into a "o"? Is there a header to add, or some control characters
> to insert?

Are you using a ucom driver that has a ucom_write method?