[lkml]   [2007]   [Oct]   [28]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
Messages in this thread
    SubjectRe: [PATCH] Dell laptop backlight driver
    Matt Domsch wrote:
    > On Sun, Oct 28, 2007 at 05:12:37PM +0100, wrote:
    >> Hello,
    >> this driver implements backlight control on Dell laptops
    >> which use SMI for changing brightness levels.
    >> The driver is INCOMPLETE since it is unable to probe some required
    >> parameters
    >> in order to perform backlight control. Such parameters are found in a Dell
    >> proprietary DMI table which should be parsed. For now external tools may be
    >> used to find these parameters by hand. So if you intend to try this out,
    >> FIRST write your laptop model parameters correctly inside the source code
    >> as explained in Documentation/dell-laptop.txt.
    >> Parts of this driver may also be used to provide additional functionalities
    >> similarly to the drivers/misc/*-laptop.c drivers.
    > Why is this better done in the kernel rather than in userspace with
    > libsmbios as you've noted?

    I had to do a kernelspace driver for controlling the backlight. This
    was part of a college project assignment. In order for it to be valid
    for an operating system course, it had to be in kernelspace (not
    Unix programming) :).

    As i mentioned that can be done in userspace and it IS sensible to do
    so. I know that the code which was already written for Dell implied
    a userspace approach, but i simply had no choice.

    I also don't expect this driver to become mainstream, but since i have
    written it, other people might want to have a look at it.

    Finally i really don't think there's any sensible way of implementing
    Linux LCD Backlight Abstraction relying on a userspace application.
    That would mean the kernel calling userspace code to change the
    brightness, then this latter code would again call the kernel to trigger
    a SMI and so on. That's just not a good design. I think a userspace
    solution implies choosing NOT to implement the LCD Abstraction. Causing
    Dell laptops to be treated differently from other machines (as they are
    not compliant with Linux's own interface).


    To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
    the body of a message to
    More majordomo info at
    Please read the FAQ at

     \ /
      Last update: 2007-10-28 18:25    [W:0.022 / U:46.648 seconds]
    ©2003-2016 Jasper Spaans. hosted at Digital OceanAdvertise on this site