From mboxrd@z Thu Jan 1 00:00:00 1970 From: Matthias Kaehlcke Subject: [PATCH 0/4] backlight: Expose brightness curve type through sysfs Date: Thu, 13 Jun 2019 12:43:22 -0700 Message-ID: <20190613194326.180889-1-mka@chromium.org> Mime-Version: 1.0 Content-Transfer-Encoding: 8bit Return-path: Sender: linux-kernel-owner@vger.kernel.org To: Thierry Reding , Lee Jones , Daniel Thompson , Jingoo Han , Bartlomiej Zolnierkiewicz Cc: linux-pwm@vger.kernel.org, dri-devel@lists.freedesktop.org, linux-fbdev@vger.kernel.org, linux-kernel@vger.kernel.org, Enric Balletbo i Serra , Douglas Anderson , Brian Norris , Pavel Machek , Jacek Anaszewski , Matthias Kaehlcke List-Id: dri-devel@lists.freedesktop.org Backlight brightness curves can have different shapes. The two main types are linear and non-linear curves. The human eye doesn't perceive linearly increasing/decreasing brightness as linear (see also 88ba95bedb79 "backlight: pwm_bl: Compute brightness of LED linearly to human eye"), hence many backlights use non-linear (often logarithmic) brightness curves. The type of curve is currently opaque to userspace, so userspace often relies on more or less reliable heuristics (like the number of brightness levels) to decide whether to treat a backlight device as linear or non-linear. Export the type of the brightness curve via a new sysfs attribute. Matthias Kaehlcke (4): MAINTAINERS: Add entry for stable backlight sysfs ABI documentation backlight: Expose brightness curve type through sysfs backlight: pwm_bl: Set scale type for CIE 1931 curves backlight: pwm_bl: Set scale type for brightness curves specified in the DT .../ABI/testing/sysfs-class-backlight | 32 +++++++++++++++++++ MAINTAINERS | 2 ++ drivers/video/backlight/backlight.c | 22 +++++++++++++ drivers/video/backlight/pwm_bl.c | 30 ++++++++++++++++- include/linux/backlight.h | 10 ++++++ 5 files changed, 95 insertions(+), 1 deletion(-) create mode 100644 Documentation/ABI/testing/sysfs-class-backlight -- 2.22.0.rc2.383.gf4fbbf30c2-goog