Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752343AbXBDN4L (ORCPT ); Sun, 4 Feb 2007 08:56:11 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1752346AbXBDN4L (ORCPT ); Sun, 4 Feb 2007 08:56:11 -0500 Received: from 2-1-3-15a.ens.sth.bostream.se ([82.182.31.214]:51915 "EHLO zoo.weinigel.se" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752343AbXBDN4K (ORCPT ); Sun, 4 Feb 2007 08:56:10 -0500 X-Greylist: delayed 1615 seconds by postgrey-1.27 at vger.kernel.org; Sun, 04 Feb 2007 08:56:09 EST To: Greg KH Cc: Andrew Lyon , linux-kernel@vger.kernel.org Subject: Re: Free Linux Driver Development! References: <20070130012904.GA9617@kroah.com> <20070130203039.GA23370@kroah.com> From: Christer Weinigel Organization: Weinigel Ingenjorsbyra AB Date: 04 Feb 2007 14:29:13 +0100 In-Reply-To: <20070130203039.GA23370@kroah.com> Message-ID: User-Agent: Gnus/5.09 (Gnus v5.9.0) Emacs/21.4 MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2325 Lines: 42 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. So the comment "The USB subsystem has changed a lot over time, and it has been possible to create userspace USB drivers using usbfs/libusb/gadgetfs that operate as fast as the USB bus allows." from feature-removal-schedule.txt is wrong I think. :-( Personally I'd much prefer to release the driver as open source, but as a consultant you don't get to decide what the customer does. So now they sit there with a driver that warns them that it'll stop working after february 2008. On a different topic, my personal pet peeve is USB scanners. There seems to be just a handful of different manufacturers of chips used in USB scanners: Realtek and Genesys covers 90% of the scanners. The SANE team has done a wonderful job of reverse engineering a lot of scanners, but the models change so fast that there seems to be no chance of keeping up. If the chip manufacturers just released specs for their chips and the scanner manufacturers could then document what settings to use Linux could have support for almost all USB scanners on the market, and it would probably cost them very little to do that. If I could find a good (4800-9600 dpi) scanner which said "supported by SANE" on the box I'd buy it immedately. /Christer -- "Just how much can I get away with and still go to heaven?" Christer Weinigel http://www.weinigel.se - 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/