From: Aaron Lu <aaron.lu@intel.com>
To: Chris Wilson <chris@chris-wilson.co.uk>,
Daniel Vetter <daniel@ffwll.ch>,
Nico Schottelius <nico-bugzilla.kernel.org@schottelius.org>,
"intel-gfx@lists.freedesktop.org"
<intel-gfx@lists.freedesktop.org>,
"dri-devel@lists.freedesktop.org"
<dri-devel@lists.freedesktop.org>
Subject: Re: [Intel-gfx] [PATCH v2] drm/i915: restore backlight precision when converting from opregion
Date: Mon, 05 May 2014 09:40:00 +0800 [thread overview]
Message-ID: <5366EBF0.8090607@intel.com> (raw)
In-Reply-To: <20140504104109.GB22557@nuc-i3427.alporthouse.com>
On 05/04/2014 06:41 PM, Chris Wilson wrote:
> On Sun, May 04, 2014 at 03:31:01PM +0800, Aaron Lu wrote:
>> On 05/04/2014 03:22 PM, Chris Wilson wrote:
>>> Also this still has the same rounding error as before.
>>
>> I didn't get this, care to explain?
>
> The calculation you use, truncates, rather than say round to nearest,
> would is the same discrepancy in your changelog.
This patch is meant to fix the problem that when user specify the max
backlight level in acpi_video interface, we will get the hardware max
level too in i915. With this patch, the hardware level we will get is:
level * freq / max = 255 * 937 / 255 = 937, which is correct.
For other values, the truncates is OK:
254 * 937 / 255 = 933
253 * 937 / 255 = 929
... ...
next prev parent reply other threads:[~2014-05-05 1:40 UTC|newest]
Thread overview: 9+ messages / expand[flat|nested] mbox.gz Atom feed top
2014-04-28 3:19 [PATCH] drm/i915: restore backlight precision when converting from opregion Aaron Lu
2014-04-28 13:41 ` Daniel Vetter
2014-05-04 7:16 ` [PATCH v2] " Aaron Lu
2014-05-04 7:22 ` Chris Wilson
2014-05-04 7:31 ` Aaron Lu
2014-05-04 10:41 ` Chris Wilson
2014-05-05 1:40 ` Aaron Lu [this message]
2014-05-12 8:55 ` [PATCH v3] " Aaron Lu
2014-05-15 8:59 ` Jani Nikula
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