From mboxrd@z Thu Jan 1 00:00:00 1970 Return-path: Received: from banach.math.auburn.edu ([131.204.45.3]:43299 "EHLO banach.math.auburn.edu" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1758029Ab1FJWoe (ORCPT ); Fri, 10 Jun 2011 18:44:34 -0400 Date: Fri, 10 Jun 2011 17:46:16 -0500 (CDT) From: Theodore Kilgore To: Alan Stern cc: Felipe Balbi , Hans de Goede , linux-usb@vger.kernel.org, Sarah Sharp , linux-media@vger.kernel.org, libusb-devel@lists.sourceforge.net, Alexander Graf , Gerd Hoffmann , hector@marcansoft.com, Jan Kiszka , Stefan Hajnoczi , pbonzini@redhat.com, Anthony Liguori , Jes Sorensen , Oliver Neukum , Greg KH , Mauro Carvalho Chehab , Clemens Ladisch , Jaroslav Kysela , Takashi Iwai , Laurent Pinchart Subject: Re: Improving kernel -> userspace (usbfs) usb device hand off In-Reply-To: Message-ID: References: MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII List-ID: Sender: On Fri, 10 Jun 2011, Alan Stern wrote: > On Fri, 10 Jun 2011, Felipe Balbi wrote: > > > I don't see any problems in this situation. If, for that particular > > product, webcam and still image functionality are mutually exclusive, > > then that's how the product (and their drivers) have to work. > > > > If the linux community decided to put webcam functionality in kernel and > > still image functionality on a completely separate driver, that's > > entirely our problem. > > And the problem is how to coordinate the two of them. > > > > 2. Until recently in the history of Linux, there was an irreconcilable > > > conflict. If a kernel driver for the video streaming mode was present and > > > installed, it was not possible to use the camera in stillcam mode at all. > > > Thus the only solution to the problem was to blacklist the kernel module > > > so that it would not get loaded automatically and only to install said > > > module by hand if the camera were to be used in video streaming mode, then > > > to rmmod it immediately afterwards. Very cumbersome, obviously. > > > > true... but why couldn't we combine both in kernel or in userspace > > altogether ? Why do we have this split ? (words from a newbie in V4L2, > > go easy :-p) > > I think the problem may be that the PTP protocol used in the still-cam > mode isn't suitable for a kernel driver. Or if it is suitable, it > would have to be something like a shared-filesystem driver -- nothing > like a video driver. You certainly wouldn't want to put it in V4L2. > > > Or, to move the libgphoto2 driver to kernel, combine it in the same > > driver that handles streaming. No ? > > No. Something else is needed. > > Alan Stern > Agreed. Something else is needed. But what? Also, very good point about PTP. Theodore Kilgore