From mboxrd@z Thu Jan 1 00:00:00 1970 From: "Tosoni" Subject: RE: Suggested patch for linux Date: Mon, 4 Aug 2008 15:28:05 +0200 Message-ID: <014d01c8f635$ee178ec0$2e01a8c0@acksys.local> References: Mime-Version: 1.0 Content-Type: text/plain; charset="US-ASCII" Content-Transfer-Encoding: 7bit Return-path: Received: from smtp01.msg.oleane.net ([62.161.4.1]:45011 "EHLO smtp01.msg.oleane.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753377AbYHDNzc (ORCPT ); Mon, 4 Aug 2008 09:55:32 -0400 In-Reply-To: Sender: linux-serial-owner@vger.kernel.org List-Id: linux-serial@vger.kernel.org To: 'Grant Edwards' , linux-serial@vger.kernel.org > -----Original Message----- > From: Grant Edwards > Sent: Thursday, July 10, 2008 4:48 PM ... > > On 2008-07-10, Alan Cox wrote: ... > > Do we really benefit from having this in kernel ? > > People who do industrial communications sure would. I maintain > a couple serial drivers that support half-duplex mode exactly > as described by the OP, and we have to control that feature via > non-standard hacks. ... I fully agree with Grant Edwards. I, as well, have been myself maintaining two serial drivers that support half-duplex mode exactly as described, and I have to control that feature via non-standard hacks !!! I have been porting them over and over again with each Linux version and subversion, since Linux 2.2, and there IS a demand for it. About the benefit to have this in the kernel: well, we would be enabled to implement it for any UART, not just the 16550 series ! Now, about Linux RT and response times: The TXD-to-RTS delay must be as short as possible. To do this, several UARTS i.e. (Ox950) have a special mode. How could you do this in a user land program for any baud rate ? I speak about baud rates up to 2 Mbps, they are in use nowadays on RS2422/RS485 lines. Really, I would like AT LEAST some commonly defined way to activate this behaviour. Russell King once suggested to create a line discipline to handle the RTS, but even like this we need a way (an ioctl) to activate the behaviour in the UART driver, to make it independent from the specific UART. JP Tosoni Acksys