HAL and the "set" functionality

Joseph Farmer jfarmer99 at yahoo.com
Wed Jun 2 18:04:18 PDT 2004

     Sorry for the noise.  I've been lurking and
following the discussions about setting hardware
settings.  I know, ideas are cheap - show us the code.
 In a minute.
     Rather than having HAL contain all of that
functionality, would the following be
     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.  If no plug-in exists for a
device, the system could return "-ERNOPLUGIN" or
somesuch.  If the plug-in is present, HAL would need a
way to export the methods that the plug-in provides.
    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.  HAL on the other hand could have
a plug-in for the printer that exports that one method
"Clean-head."  Setserial could become a plugin as
could the ability to set IRQs on some older ISAPNP
stuff.  HAL wouldn't do policy - the plug-ins would. 
The plug-ins would be a frontend to programs that
could also have a CLI.  hdparms is another example. 
This is all hardware specific (unlike IP address). 
Setting a netcard to full-duplex, loading soft fonts
into an AWE, sending an AT&F to a modem, the list goes
on.  If plug-ins don't appear, not much lost.
     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.
     Sorry if Yahoo wraps this funny.  I'm going to
have to re-register my domain one of these days for

Do you Yahoo!?
Friends.  Fun.  Try the all-new Yahoo! Messenger.

hal mailing list
hal at freedesktop.org

More information about the Hal mailing list