HAL and the "set" functionality

Joe Shaw joeshaw at novell.com
Thu Jun 3 12:28:04 PDT 2004


On Wed, 2004-06-02 at 18:04 -0700, Joseph Farmer wrote:
>      A plug-in system.  HAL could scan plug-ins to see
> if any are available.  The plug-in would have a method
> of stating what devices it can handle (PCI ID, USB ID,
> etc) and there would be a global "flag" for the
> plug-in being present.

A plug-in system isn't really all that different from what we were doing
before, except that they were all built-in. :)  I think that bloat in a
daemon that's going to be always running is a valid concern, and plug-
ins definitely don't help that.

>     I've seen that Robert is big on use cases (good
> thing too).  Here is the one that immediately came to
> mind.  I have an Epson Stylus Color 400 printer.  CUPS
> can deal with print functionality.  CUPS has no way to
> trigger a "printhead clean" option.  The Windows
> driver from Epson has this.  It really has nothing to
> do with printing so I can't see where this should be
> in the print driver.  

I'd disagree that it doesn't really have anything to do with printing.
CUPS is really more than just the print spooler; it's the interface
between the printer hardware and the software on top of it.  And simply
because of the way the software is today I don't think it's possible (or
necessarily a good idea) to divorce the printer driver from CUPS.

That all said, I think the functionality is worthwhile, but it probably
makes most sense in a library by itself.  That way apps could still use
a single API to do it, but it wouldn't require the HAL daemon to be
running or have the special plugin.  And since it'll all need to go
through CUPS anyway, there's not an added level of indirection if it's
not needed.

>      GStreamer, ALSA, etc took the plug-in route.  I
> think it would work.  My ability to hack on HAL isn't
> going to be up to snuff but plug-ins I can do.

I dunno much about ALSA, but I've found all the plugins to be irritating
in GStreamer.  That's not to say that it's not a good piece of software,
but you need to be sure to have all these plugins installed to be able
to play a simple audio file.  Perhaps it's just a packaging issue, but
it's error prone and has caused me no small amount of grief in the past.


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