Bug with 2.6 serial driver when in UART 8250 mode
From: Alexandre Courbot
Date: Wed Aug 04 2004 - 07:36:16 EST
Hello everybody,
For communicating with a serial device of ours we need to disable the
UART buffer (the device at the other end doesn't have a serial buffer at
all and therefore we can't use hardware control flow efficiently). The
only way to do this with Linux seems to pass the UART in 8250 mode,
which doesn't use the buffer:
# setserial /dev/ttyS0 uart 8250
We did that with success with 2.4 kernel series. Since most of our
machines are using 2.6, we tried to do the same on them, but noticed
something wrong: only one byte upon 16 is being sent. For instance, if I
$ echo -n "qwertyuiopasdfgh" > /dev/ttyS0
My device only receives the 'h', while with a 2.4 kernel it receives the
entire string.
So I think that for some reason, the UART buffer is not deactivated
while switching it to 8250 mode, and that the driver only sends the last
byte it contains when the interrupt is triggered.
I've tried to look at the code but unfortunately only lost myself
without being able to even identify the right source file to look at.
Sorry about that. :/
Could someone have a look at this or point me to the right section of
code so I do it myself?
Thanks,
Alex.
PS: please CC replies as I'm not subscribed to the list.
--
Alexandre Courbot
PhD Student - LIFL/RD2P
http://www.lifl.fr/~courbot/
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