From mboxrd@z Thu Jan 1 00:00:00 1970 From: Corey Minyard Subject: Re: Serial 8250: clear the lsr_break_flag at open Date: Thu, 03 May 2007 22:43:19 -0500 Message-ID: <463AABD7.7090903@acm.org> References: <20070430220858.GA28890@localdomain> <20070501092933.GB18233@flint.arm.linux.org.uk> <46373F42.4080305@acm.org> <20070503120815.GA21024@flint.arm.linux.org.uk> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Return-path: Received: from mta16.adelphia.net ([68.168.78.211]:35225 "EHLO mta16.adelphia.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1767652AbXEDDnX (ORCPT ); Thu, 3 May 2007 23:43:23 -0400 In-Reply-To: <20070503120815.GA21024@flint.arm.linux.org.uk> Sender: linux-serial-owner@vger.kernel.org List-Id: linux-serial@vger.kernel.org To: Russell King , Linux Kernel , linux-serial@vger.kernel.org Russell King wrote: > > The backup code is something I never properly reviewed, so no comments > there. The tx_empty code I assumed would be a relatively rare event, > except when closing the port (at which point you don't particularly care > about errors anyway, not even the break flag since chances are you'll > miss the following character.) > That "if" statement in the backup code does look a little dodgy, more than is perhaps required. I think it's correct, but I need to add a lock there in my patch to protect the LSR check. > Given that people might want to poll it for various reasons, I guess > saving the status away should be done. However, there's a slight issue > with working out which character the error is associated with. Careful > locking may be the answer to that though. > I think as long as you hold the port lock while you grab the LSR and set the saved flags it will work. > As for start_tx, yes, though slightly harder to check. Maybe the code > should be modified to reduce the number of potential LSR reads by reading > the IIR first, and only if that shows no interrupt pending should the LSR > be read (and the error flags remembered.) > The version of start_tx in 2.6.21 does check IIR first, and it only checks the LSR if UART_BUG_TXEN is set, so I assume that's not a big deal. I'll sleep on it tonight, look it over tomorrow morning, and resend the patch. Thanks, -corey