Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752467AbXBDSUT (ORCPT ); Sun, 4 Feb 2007 13:20:19 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1752477AbXBDSUT (ORCPT ); Sun, 4 Feb 2007 13:20:19 -0500 Received: from cantor.suse.de ([195.135.220.2]:51822 "EHLO mx1.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752467AbXBDSUR (ORCPT ); Sun, 4 Feb 2007 13:20:17 -0500 Date: Sun, 4 Feb 2007 10:19:12 -0800 From: Greg KH To: Christer Weinigel Cc: Andrew Lyon , linux-kernel@vger.kernel.org Subject: Re: Free Linux Driver Development! Message-ID: <20070204181912.GA12379@kroah.com> References: <20070130012904.GA9617@kroah.com> <20070130203039.GA23370@kroah.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.5.13 (2006-08-11) Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1375 Lines: 32 On Sun, Feb 04, 2007 at 02:29:13PM +0100, Christer Weinigel wrote: > Greg KH writes: > > > Why would a userspace driver not work out for this. We already can > > saturate the USB bus with a userspace program > > That is unfortunately not quite true. I have a (unfortunately > proprietary) driver for a USB device that simply cannot be implemented > in userspace. The USB device is a measurement device that pushes > close to 800 kBytes/second of data through a FT245 chip. The > measurement device does no flow control at all, it just presents a > sample every 125 us to the FT245 and with only 256 bytes of buffer in > the FT245 the only way to handle that is to have two URBs in flight at > the same time, and I haven't found any way to do that in a robust and > non-racey way from userspace. People do that today just fine with multiple userspace urbs in flight using usbfs directly. So it is possible and can be done. If there are issues with the usbfs code to prevent you from doing this, please let us know. Or perhaps your device just needs to add some flow control to it :) good luck, greg k-h - 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/