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    SubjectRe: 2.0.30 serial.c, ppp.c and pppd-2.2 questions
    On 24-Jul-97 Theodore Y. Ts'o wrote:
    >I just finished taking a quick look at Rob's patches, and besides some
    >design problems I have with it (if you specify an FIFO size which isn't
    >supported by your UART, it silently turns the FIFO completely *OFF*,

    If you are refering to the fact that large switch contruct that
    does nothing in the default (bad trigger level) case, I did
    that on purpose. The code that checks the validity of the FIFO
    size is in set_serial_info() and does work properly. I wanted
    to make sure that if the logic in that piece was wrong, or that
    I had made a mistake in setting the default trigger levels, I
    would notice it immediately.

    >which may be a bit surprising to the user), there's one big problem with
    >the patch.
    >It currently works by scheduling a post-flush tqueue handler which
    >enables RTS and RDI if they had previously been disabled. This is a
    >problem, because the line discpline may have cleared RTS because its
    >upper level buffering had filled. So simply always enabling RTS after
    >the line discpline flush is a bad thing, and may result in significant
    >numbers if the line discpline needed to exert flow control for some
    >reason. This isn't an issue with PPP (which is probably why Rob didn't
    >think of it), but it is an issue with the N_TTY line discpline.

    No, I just forgot :)

    I noticed it early on in the development, realized it would
    not impact me and ignored it. I did not expect to be publishing
    a patch, so I let it slip my mind.

    >So I wouldn't apply this patch at all if you use any non-PPP
    >applications on your serial lines (i.e., dialup login, UUCP, etc.)

    Good advise for now. I will try to get that fixed ASAP.


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