From mboxrd@z Thu Jan 1 00:00:00 1970 From: Greg KH Date: Tue, 17 Feb 2004 01:39:05 +0000 Subject: Re: Hotplug-- who notifies whom of what? Message-Id: <20040217013905.GA3596@kroah.com> List-Id: References: <40316638.9060501@earthlink.net> In-Reply-To: <40316638.9060501@earthlink.net> MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit To: linux-hotplug@vger.kernel.org On Mon, Feb 16, 2004 at 06:54:16PM -0600, Bryan W. Headley wrote: > Greg, > > Regards to Aiptek USB tablets... > > I'm trying to figure out a strategy for hotplugging. > > 1) The tablet is mapped to the input device system. > a) Because the order in which drivers complete loading/registering > is not deterministic (e.g., mouse driver spawns thread), I do not > know with certainty that the tablet will always be mapped to > /dev/input/event27. So, configuration files of certain (XFree) > applications that require that the path be known and static enough > to put in a text file. Use udev to always create your "/dev/input/tablet_mine_all_mine" node so that XFree does not have to be reconfigured all the time. > b) No problem. So I whip up a startup process that finds the tablet > and creates a softlink that XF86Config-4 can refer to. That is > relying on the sysvinit system, and is wrong insofar as it knows > there's a tablet owned by the user (I'm thinking of RH, Mandrake, > et al, quality scripts, here. Not little one-liners we all write.) Sure, create a symlink in udev instead. It can do that just fine if you don't want to use a "real" node. > 2) In case of a hotplug event, e.g., the tablet being disconnected, I > really should get rid of the softlink... > a) But is that the domain of a script in hotplug? Nope, that's udev's job. > 3) In case of hotplug-connect, I should re-create the softlink. udev does that for you just fine. > a) Again, in the hotplug domain? I ask because I have an rc script > that does the same thing on boot-up, and I'd rather not have > things cross-referenced between two packages. > b) Plus, what I do to find the aiptek tablet COULD BE scriptable on > 2.6, would be hard to script on 2.4. Anyway, it's not a script > now, it makes ioctl calls. > > 4) Moving upstream... X needs to be notified that device 'x', that it's > using for input, has been plugged/unplugged. No facility for that, > except in my xf86aiptek device driver for X, which DOES have a > bidirectional communications channel, which could have a "Unwind > driver" API call > a) Right now, the only thing that knows my API is my user-friendly > front-end. It's not something you'd run as a daemon... > b) But a subset of it certainly could. Question is, what does it > listen for? Hotplug messages forwarded off of dbus? Does it > monitor Hal? Is it really something that's fired off directly > by hotplug? Or owned by hotplug? How about listening to dbus messages? That is the way that both GNOME and KDE are moving to using. > 5) Does udev fit into this conversation anywhere? It can be hotplug, > dbus, or hal-aware, or do it's thing by itself... Yes it does, see above. Hope this helps, greg k-h ------------------------------------------------------- SF.Net is sponsored by: Speed Start Your Linux Apps Now. Build and deploy apps & Web services for Linux with a free DVD software kit from IBM. Click Now! http://ads.osdn.com/?ad_id56&alloc_id438&op=click _______________________________________________ Linux-hotplug-devel mailing list http://linux-hotplug.sourceforge.net Linux-hotplug-devel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/linux-hotplug-devel