Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1758791Ab3EDLqF (ORCPT ); Sat, 4 May 2013 07:46:05 -0400 Received: from smtp46.i.mail.ru ([94.100.177.106]:54265 "EHLO smtp46.i.mail.ru" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752022Ab3EDLqB (ORCPT ); Sat, 4 May 2013 07:46:01 -0400 Message-ID: <51850295.6020601@list.ru> Date: Sat, 04 May 2013 16:44:05 +0400 From: Stas Sergeev User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:17.0) Gecko/20130311 Thunderbird/17.0.4 MIME-Version: 1.0 To: Johan Hovold CC: Greg KH , Jarkko Huijts , Alan Cox , linux-usb@vger.kernel.org, linux-serial@vger.kernel.org, Linux kernel , Caylan Van Larson , "Rafael J. Wysocki" Subject: Re: Regression: ftdi_sio is slow (since Wed Oct 10 15:05:06 2012) References: <5183D196.2080305@list.ru> <20130503163008.GA30699@kroah.com> <5183F62A.1020801@list.ru> <20130503165231.GA1966@kroah.com> <5183FC83.8090602@list.ru> <20130503171618.GA16686@kroah.com> <51840186.7000608@list.ru> <20130503203419.GA25932@kroah.com> <51843132.9040304@list.ru> <20130504111535.GC16818@localhost> In-Reply-To: <20130504111535.GC16818@localhost> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit X-Spam: Not detected X-Mras: Ok Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1110 Lines: 20 04.05.2013 15:15, Johan Hovold пишет: > The query takes longer than the transmit at decent baudrates (>=38k) > and under the assumption that flow control isn't causing any delays. > > But you do have a point, and I have been meaning to look into whether > the added overhead of checking the hardware buffers could be mitigated > by adding wait_until_sent support to usb-serial. This way the we would > only query the hardware buffers on tty_wait_until_sent (e.g. at close) > and select and TIOCMOUTQ would not suffer. This is also the way things > are handled in serial_core. Thanks for taking a look. Indeed, it seems .wait_until_sent is the best candidate for that kind of things, and the patch in question would even match its description be it using .wait_until_sent and not .chars_in_buffer. Please count on testing your patches here when they are ready. -- 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/