> -----Original Message----- > From: Daniel Vetter [mailto:daniel.vetter@xxxxxxxx] On Behalf Of Daniel Vetter > Sent: Tuesday, September 30, 2014 10:23 AM > To: Eoff, Ullysses A > Cc: Daniel Vetter; intel-gfx@xxxxxxxxxxxxxxxxxxxxx > Subject: Re: [PATCH 1/2 v3] drm/i915: intel_backlight scale() math WA > > On Tue, Sep 30, 2014 at 04:52:43PM +0000, Eoff, Ullysses A wrote: > > > -----Original Message----- > > > From: Daniel Vetter [mailto:daniel.vetter@xxxxxxxx] On Behalf Of Daniel Vetter > > > Sent: Tuesday, September 30, 2014 9:32 AM > > > To: Eoff, Ullysses A > > > Cc: daniel@xxxxxxxx; intel-gfx@xxxxxxxxxxxxxxxxxxxxx > > > Subject: Re: [PATCH 1/2 v3] drm/i915: intel_backlight scale() math WA > > > > > > On Tue, Sep 30, 2014 at 02:58:54PM +0000, Eoff, Ullysses A wrote: > > > > On Tue, 2014-09-30 at 10:04 +0200, Daniel Vetter wrote: > > > > > On Mon, Sep 29, 2014 at 03:49:32PM -0700, U. Artie Eoff wrote: > > > > > > Improper truncated integer division in the scale() function causes > > > > > > actual_brightness != brightness. This (partial) work-around should be > > > > > > sufficient for a majority of use-cases, but it is by no means a complete > > > > > > solution. > > > > > > > > > > > > TODO: Determine how best to scale "user" values to "hw" values, and > > > > > > vice-versa, when the ranges are of different sizes. That would be a > > > > > > buggy scenario even with this work-around. > > > > > > > > > > > > The issue was introduced in the following (v3.17-rc1) commit: > > > > > > > > > > > > 6dda730 drm/i915: respect the VBT minimum backlight brightness > > > > > > > > > > > > v2: (thanks to Chris Wilson) clarify commit message, use rounded division > > > > > > macro > > > > > > > > > > > > v3: -DIV_ROUND_CLOSEST() fails to build with CONFIG_X86_32=y. (Jani) > > > > > > -Use DIV_ROUND_CLOSEST_ULL() instead. (Damien) > > > > > > -v1 and v2 originally authored by Joe Konno. > > > > > > > > > > > > Signed-off-by: U. Artie Eoff <ullysses.a.eoff@xxxxxxxxx> > > > > > > > > > > Is there some bug report, internal jira, mailing list reference or similar > > > > > about this? > > > > > > > > > > Note that at least for OTC jira tasks we now want them to be added to > > > > > commit message with e.g. > > > > > > > > > > OTC-Jria: VIZ-4932 > > > > > > > > > > > > > Yes, the OTC-Jira task is: VIZ-4395. I'll resubmit with amended commit > > > > message. > > > > > > > > > And I guess I should merge patch 2 before patch 1, right? > > > > > > > > No, patch 1 before patch 2. > > > > > > Oh, I didn't notice that your first add a duplicated version of the macro > > > and then unify it. That's a bit backwards ... > > > > The reason for doing it this way is so we can cherry-pick patch 1 into the > > chromeos 3.10 kernel cleanly (with some other backlight patches). > > That is, patch 1 is decoupled from the changes in intel_display.c. > > Hope that makes sense. > > Yeah. Would be good to mention that in the commit message, e.g. "For > easier backporting Duplicate the division macro here and refactor the code > in a follow-up patch". I'll add that when merging if you don't resend. Agreed. I'll let you amend the message while merging if you don't mind. I'll get the process right in another round ;-) Thanks for your support! U. Artie > -Daniel > -- > Daniel Vetter > Software Engineer, Intel Corporation > +41 (0) 79 365 57 48 - http://blog.ffwll.ch _______________________________________________ Intel-gfx mailing list Intel-gfx@xxxxxxxxxxxxxxxxxxxxx http://lists.freedesktop.org/mailman/listinfo/intel-gfx
