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SubjectRe: [PATCH] [RESEND] Add Dell laptop backlight brightness display
On Tue, Feb 07, 2006 at 01:37:06PM +0000, Richard Purdie wrote:
> On Tue, 2006-02-07 at 13:23 +0000, Matthew Garrett wrote:
> > Would you be open to adding generic support for displaying separate AC
> > and DC brightnesses? Making it driver specific leaves the potential for
> > inconsistencies.
>
> The problem is that AC or DC is not a generic property of backlights but
> specific to your problematic hardware case. You're going to have a to
> find a way to tell if its running on AC or not to report the right value
> in the manner the class requires.

Cases rather than case, sadly. Determining whether the hardware is on AC
or not tends to be much more awkward than you'd think. On HPs, it seems
to be done by making a specific call to the embedded controller. This is
very model specific, whereas the brightness values aren't. It's also
likely to go horribly wrong if the hardware is trying to access the
embedded controller at the same time. Realistically, it's impossible
without making the driver depend on ACPI and exporting acpi_ac_get_state
from the ACPI layer, which would be a shame since the rest of the
functionality isn't ACPI dependent at all.

> I can't see how you plan to add "generic support for displaying separate
> AC and DC brightnesses" without destroying the point of the class (which
> for the brightness parameter is to display the current backlight
> brightness).

I think providing a consistent interface for what information we can
provide is worthwhile.

--
Matthew Garrett | mjg59@srcf.ucam.org
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