[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:0.058 / U:6.556 seconds]
©2003-2018 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site