Hal or dbus info
chuckr at telenix.org
Tue Jun 17 00:28:33 UTC 2008
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Joe Marcus Clarke wrote:
> On Mon, 2008-06-16 at 15:34 -0400, Chuck Robey wrote:
> Anyone know, in the case of FreeBSD, how Hal gets (or, I suppose, dbus gets) the
> usb device info? I am writing an Xorg Xinput driver for a USB graphic tablet,
> and I need to instrument the Hal & dbus interface for it. I think I will be
> able to get away with (as far as a purely FreeBSD portion) using the uhid
> driver, so I don't need to write any FreeBSD driver. However, using my tools at
> hand, I get the feeling that hal doesn't get realtime data for usb plugging info.
>> Hal reads the USB data from /dev/usb using the FreeBSD USB API. It
>> learns about hot-plugged USB devices from devd.
> Reason I say that Hal knows usb is because I can use lshal, and list all of the
> current usb devices. However, if I use dbus-monitor to watch teh dbus state in
> realtime, then I unplug & plug my graphic tablet, dbus monitor is slient about
> it, even if I wait 30 minutes.
>> You would need to monitor the system dbus channel.
> So, I want to find out what's the source of dbus's info about the state of the
> USB devices. It's gotta get this info somehow. Alex Leidinger suggested you
> (and I am running Gnome here, it's possible my Hal is learning all this via Gnome).
>> D-BUS really has nothing to do with this. Hald is responsible for
>> learning about the various hardware components. It only uses D-BUS to
>> communicate that data to clients.
> You see, if I'm not able to make myself happy with whatever I find, I may well
> write some kind of a app to run from devfs or devd (which seems to know this
> stuff in realtime) to tip off dbus. However, if it's Gnome, maybe the
> possibility exists to configure Gnome to know more?
>> Hald already connects to devd, so it should receive realtime updates.
>> You might want to look at the hal API, and use the FreeBSD hald addons
>> as a guide (i.e. take a look at the storage addon). You can use dbus
>> filters to pick up hal messages about various devices.
Thanks, Joe. Between what I got in mail, and what I got in reading all three
specs (hal, dbus, and policykit), and the Xinput-hotplugging wiki, I got
everything I need now. You won't hear from me for a short while now, while I
Sure do appreciate everything I got.
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