Re: [PATCH] Rationalise ACPI backlight implementation

[Andrew Morton <akpm@linux-foundation.org>]

> On Thu, 24 Jan 2008 16:44:48 -0500 Len Brown <lenb@kernel.org> wrote:
> On Tuesday 25 December 2007 21:03, Matthew Garrett wrote:
> > The sysfs backlight class provides no mechanism for querying the 
> > acceptable brightness for a backlight. The ACPI spec states that values 
> > are only valid if they are reported as available by the firmware. Since 
> > we can't provide that information to userspace, instead collapse the 
> > range to the number of actual values that can be set.
> > 
> > Signed-off-by: Matthew Garrett <mjg59@srcf.ucam.org>
> 
> I wish we did this in the first place.
> But doing it now is an API change -- since
> with the old way 100 always meant 100% brightness, yes?
> 
> so my concern is that if we change what "10" means, somebody like akpm
> with an existing script gets grumpy.

It takes more than that to make me grumpy.  I've been very grumpy lately.

- Create a new /sys node with a new name which has the new semantics.

- Deprecate the old /sys entry by emitting an angry printk when someone
  uses it.

- Wait 12 months

- Kill the old one.