[RFC] dev_acpi: support for userspace access to acpi

From: Alex Williamson (alex.williamson_at_hp.com)
Date: 10/26/04

  • Next message: Helge Hafting: "Re: HARDWARE: Open-Source-Friendly Graphics Cards -- Viable?" 
    To: linux-kernel <linux-kernel@vger.kernel.org>
Date:	Tue, 26 Oct 2004 14:55:00 -0600

       Announcing the next revision of dev_acpi. The dev_acpi module
    provides userspace access to ACPI namespace using a simple character
    device file. For further discussion of the interface, see the README
    file in the tarball. The current release is available here:

    http://free.linux.hp.com/~awilliam/acpi/dev_acpi/dev_acpi-20041026.tar.bz2

    (it's a little big to post here raw, but if requested I'd be happy to
    post the driver by itself)

       I've been tossing around sysfs and device file interfaces to the ACPI
    namespace for a while now. The idea is that there's way too much
    information in namespace to not provide a userspace interface to it.
    Examples include projects springing up to support ACPI features on
    various laptops, increasing dependence on developing code using ACPI,
    extracting system/platform information from ACPI namespace. In short,
    there are a lot of really simple things that userspace could use ACPI
    namespace for, but there's currently no way to get to it.

       Previous iterations using sysfs looked pretty, but never really
    achieved the full potential of the interface (no ioctl, read issues on
    files, complex data for sysfs, file per operation, etc...). The device
    file interface provides a more comprehensive yet compact interface,
    along with a 32bit compatibility layer, and sane read semantics on the
    file.

       This revision cleans up quite a bit of code, adds some documentation
    in the README file, adds a number of interfaces, and adds several more
    example program, with the intent of sparking more interest. I've
    updated the acpitree program to list a bit more data, but it's basically
    the same. For anyone trying to wrap their head around ACPI namespace,
    it's a great tool for getting a simple visual representation of the data
    available. I added a tool called acpivideo that will hopefully be
    interesting to laptop users. It's able to set the active video output
    device, much like the hotkey on most laptops (but from command line).
    It also has a daemon mode that sets up a notify handler (yes, from
    userspace) and listens for events on the VGA device. When an event is
    received, it evaluates the requested state change and pokes ACPI to do
    it. See the README for more info. If anyone knows how to poke X to not
    block the switch it'd be interesting to add the hooks (currently only
    seems to work from a vt).

       I added another simple program called acpiundock. If you have a
    laptop docking station with an electo-mechanical eject (like the
    omnibook 500), this one should be fun. There are no option, just run it
    and see what happens (please be prepared for it to work... it just
    might).

       Another fun developer tool/hack is eventwatch. This program is
    simply a version of acpitree that tries to install notify handlers on
    every device in namespace. It then sits and waits for something to
    happen. If you've wondered if that hotkey on your box does something,
    try this, it just might.

       I skimmed though the ibm-acpi module and tried to provide enough
    interfaces in this version of dev_acpi that the entire ibm-acpi could
    potentially be done in userspace. I don't have an IBM laptop to
    experiment with, but I'd be interested to hear if someone tries.

       Anyway, please give this interface a shot. It builds as a standalone
    module and should work on any 2.6 kernel with headers available. I've
    tested this version quite a bit more than the version I posted a couple
    weeks ago, especially the 32bit app on 64bit kernel code (ia64 and
    x86_64). Bug reports, feedback, opinions gladly welcomed. Thanks,

            Alex 

    -- 
Alex Williamson                             HP Linux & Open Source Lab
-
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/
  • Next message: Helge Hafting: "Re: HARDWARE: Open-Source-Friendly Graphics Cards -- Viable?"

    Relevant Pages