Re: Re[4]: Help needed on Serial driver issues

Theodore Y. Ts'o (tytso@MIT.EDU)
Thu, 22 Jan 1998 18:18:45 -0500

Date: Thu, 22 Jan 98 14:10:09 -0500
From: Shashi Ramamurthy <>

Now you were asking me about the flow control and throttle
handling in our driver. The way it works is as follows,
1. we set RTSCTS in the hardware and hardware handles it
based on the status of the buffer and control signals.

2. When the driver's throttle function is called from the line
discipline, I set a software flag for the input routine to know that
the upper layers cannot handle anymore data and it will not do any
any more input processing until it sees the software flag turned off
which will happen when unthrottle function is called.

That's what I thought you were doing; you're much better off if you keep
the amount in the board's FIFO to a minimum, and then not let the board
handle RTS automatically; instead have your driver explicitly raise and
lower RTS as appropriate.

Things will be much happier that way, trust me.....

- Ted