From mboxrd@z Thu Jan 1 00:00:00 1970 From: Daniel Thompson Date: Fri, 16 Aug 2019 15:54:18 +0000 Subject: Re: Re: [PATCH v3 2/4] backlight: Expose brightness curve type through sysfs Message-Id: <510f6d8a-71a0-fa6e-33ea-c4a4bfa96607@linaro.org> List-Id: References: <20190709190007.91260-1-mka@chromium.org> <20190709190007.91260-3-mka@chromium.org> <20190807201528.GO250418@google.com> In-Reply-To: <20190807201528.GO250418@google.com> MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit To: Matthias Kaehlcke , Thierry Reding , Lee Jones , 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 On 07/08/2019 21:15, Matthias Kaehlcke wrote: > On Tue, Jul 09, 2019 at 12:00:05PM -0700, Matthias Kaehlcke wrote: >> 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 currently is opaque >> to userspace, so userspace often uses 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 the new sysfs attribute >> 'scale'. The value of the attribute can be 'linear', 'non-linear' or >> 'unknown'. For devices that don't provide information about the scale >> of their brightness curve the value of the 'scale' attribute is 'unknown'. >> >> Signed-off-by: Matthias Kaehlcke > > Daniel (et al): do you have any more comments on this patch/series or > is it ready to land? I decided to leave it for a long while for others to review since I'm still a tiny bit uneasy about the linear/non-linear terminology. However that's my only concern, its fairly minor and I've dragged by feet for more then long enough, so: Reviewed-by: Daniel Thompson Daniel.