[Qemu-devel] hw/serial.c: Xmit fifo never used

[Frank Mehnert]

Hi,

the xmit fifo of the serial device is never used. If qemu_chr_write()
fails (interface currently not able to send characters) then the
transmit_timer should be engaged to try to send the current character
from the fifo again after some time. The code is

    } else if (qemu_chr_write(s->chr, &s->tsr, 1) != 1) {
        if ((s->tsr_retry > 0) && (s->tsr_retry <= MAX_XMIT_RETRY)) {
            s->tsr_retry++;
            qemu_mod_timer(s->transmit_timer,
                           new_xmit_ts + s->char_transmit_time);
            return;
        }
        ...
    }

The problem is that this path is never used as tsr_retry is never > 0
initially. So if qemu_chr_write() fails, we never try again but drop
the character.

I assume the correct condition would be '>= 0', that is

        ...
        if ((s->tsr_retry >= 0) && (s->tsr_retry <= MAX_XMIT_RETRY)) {
            s->tsr_retry++;
        ...

Kind regards,

Frank
-- 
Dr.-Ing. Frank Mehnert

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