Re: serial port - ioctl's prevent subsequent reads

David Monniaux (David.Monniaux@ens.fr)
Thu, 18 Nov 1999 10:09:41 +0100 (MET)


Thanks for your answer.

On Wed, 17 Nov 1999, Theodore Y. Ts'o wrote:

> That's not what CLOCAL means. Read the POSIX specification. POSIX

:-) Nobody has POSIX standards available around. I'll have it ordered by
the library.

Perhaps documenting the Linux kernel ioctl's and other settings would be a
step in the right direction. The only information I had about TIOCMGET/SET
was reading gpm sources.

> As far as the serial driver's enabling DTR when the port is opened; this

The problem is not DTR, but RTS. I don't care whether the kernel moves
DTR, but I don't understand why it would touch RTS even when we are
-crtscts (it pulls RTS low for a little period).

> I'm just assuming the
> programmer is writing good code. (Clearly that was a bad assumption.)

Writing code using functions that are NOT documented in the only help of
the system, using header files as reference, is surely error-prone.
Clearly, we need some documentation on such issues, since saying "Just
read spec XXX", where spec XXX is a document that is available for a
costly fee from an institution on the other side of the globe is NOT a
satisfactory answer.

I volunteer to write something clear on the subject of RS232 I/O under
Linux (not this week, since I'm supposed to work on my thesis).

---
David Monniaux     Tel: +33 1 44 32 20 66    Fax: +33 1 44 32 20 80 
Laboratoire d'informatique de l'École Normale Supérieure,
45 rue d'Ulm - 75230 PARIS cedex 5 - FRANCE

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