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SubjectRe: TTY Flip buffers
   Date: Wed, 24 Nov 1999 12:12:48 -0800 (PST)
From: Linux Lists <lists@cyclades.com>

Just one question: I looked at n_tty_receive_buf and I didn't see any
protection / warn back mechanism (the function is void) as to "what if the
room in the TTY buffer is too small to store all the data passed
directly by the driver". What happens if the driver passes a data amount
that's bigger than the available room in the TTY buffer??

The line discpline is responsible to calling the driver's
throttle()/unthrottle() as the space in the tty buffer goes above and
below the high and low watermarks; this is how hardware (and software)
flow control is handled.

Linux gives plenty of time (something like 768 characters, if I remember
correctly) for the sending device to stop sending characters; if the
sending device ignores the flow control, the tty layer does the only
thing it can do --- it drops the data on the floor.

- Ted

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