hal spec 0.2-pre

Alexander Larsson alexl at redhat.com
Thu Oct 30 11:20:16 EET 2003

On Thu, 2003-10-30 at 02:30, David Zeuthen wrote:
> Hi,
> I've compiled most of conclusions from several recent HAL discussion on
> this list into a new version of the HAL spec. Find it at
>   http://freedesktop.org/~hal/spec-0.2-pre/hal-spec.html

A few comments:

> * Unique ID (referred to as unique-device-id in the following)
> This is an identifier that is unique for a device object - that is, no
> other device object can have this ID at the same time. This ID is
> computed from bus-specific information so it may (but also may not)
> even be unique across device insertions and when multiple instances of
> the same kind of device is plugged in.

This reads as if its not guaranteed that multiple instances of the same
kind of device plugged in at the same time get differnt unique ids. I
hope this is just "typo". We really need to be able to address each

> # (TODO: how to implement this in D-BUS properly? What if the process locking
> #  the object dies? Ping the D-BUS service (e.g. :32-0) holding the lock on
> #  a regular basis?)
> #
> void Lock()

dbus allows you to detect when a client disconnects from the bus (if
e.g. the process died). The process could still hang, but this is at
least some level of protection. You can just kill the hanged process.

> # Create a new device object which will be hidden from applications
> # until the Commit() method is called. Returns an object that implements
> # the org.freedesktop.Hal.Device interface.

Added(), not Commit() i guess.

> BootProgram (string)

How are ';' escaped in the list? Maybe this isn't needed? If you need to
use ';' in the commands you could stuff that in a shell script.

> usb.version (double)

I don't recommend doubles for storing versions. 1.1 can't event be
represented in binary floating point, and exact comparisons on floats
should never be done.

 Alexander Larsson                                            Red Hat, Inc 
                   alexl at redhat.com    alla at lysator.liu.se 
He's a fast talking gay senator searching for his wife's true killer. She's a 
green-fingered red-headed bounty hunter with the power to see death. They 
fight crime! 

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