Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932252AbVJIKJT (ORCPT ); Sun, 9 Oct 2005 06:09:19 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1751104AbVJIKJT (ORCPT ); Sun, 9 Oct 2005 06:09:19 -0400 Received: from mailfe10.tele2.fr ([212.247.155.44]:24761 "EHLO swip.net") by vger.kernel.org with ESMTP id S1750800AbVJIKJS (ORCPT ); Sun, 9 Oct 2005 06:09:18 -0400 X-T2-Posting-ID: dCnToGxhL58ot4EWY8b+QGwMembwLoz1X2yB7MdtIiA= Date: Sun, 9 Oct 2005 12:09:09 +0200 From: Samuel Thibault To: akpm@osdl.org, Alan Cox , linux-kernel@vger.kernel.org, linux-serial@vger.kernel.org Subject: Re: [patch 3/4] new serial flow control Message-ID: <20051009100909.GF5150@bouh.residence.ens-lyon.fr> Mail-Followup-To: Samuel Thibault , akpm@osdl.org, Alan Cox , linux-kernel@vger.kernel.org, linux-serial@vger.kernel.org References: <200501052341.j05Nfod27823@mail.osdl.org> <20050105235301.B26633@flint.arm.linux.org.uk> <20051008222711.GA5150@bouh.residence.ens-lyon.fr> <20051009000153.GA23083@flint.arm.linux.org.uk> <20051009002129.GJ5150@bouh.residence.ens-lyon.fr> <20051009083724.GA14335@flint.arm.linux.org.uk> Mime-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <20051009083724.GA14335@flint.arm.linux.org.uk> User-Agent: Mutt/1.5.9i-nntp Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1788 Lines: 50 Hi, Russell King, le Sun 09 Oct 2005 09:37:24 +0100, a ?crit : > On Sun, Oct 09, 2005 at 02:21:30AM +0200, Samuel Thibault wrote: > > Russell King, le Sun 09 Oct 2005 01:01:53 +0100, a ?crit : > > > > How could this look like in userspace? > > > > > > I think they should be termios settings - existing programs know how > > > to handle termios to get what they want. > > > > Hence a new field in the termios structure? > > > > There was a discussion about this back in 2000: > > > > http://marc.theaimsgroup.com/?t=96514848800003&r=1&w=2 > > What I was thinking of was to use some of the spare termios cflag bits > to select the flow control. You'd only want one flow control type at > one time though. Eg: define two fields, each to select the signal. > > 0 - RTS > 1 - DTR > > 0 - CTS > 1 - DTR > 2 - DSR It looks fine, but it might not be sufficient for expressing that: - some flow control use RTS to indicate that DTE is ready to send data, - some other use it to indicate that DTE wants to send data. (and CTS is used for acknowledgment of this), - some other use it as a strobe for acknowledging characters, some other use it as a strobe for acknowledging frames (announced by CTS). > However, bear in mind that the majority of the more inteligent 8250- > compatible UARTs with large FIFOs only do hardware flow control on > RTS/CTS Hardward flow control is usually performed in software. Can't their hardware implementation of hardware flow control be disabled when control method is not usual RTS/CTS? Regards, Samuel - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/