From: Thierry Reding Date: Mon, 7 Apr 2014 13:45:30 +0000 (+0200) Subject: pwm: Document signal polarity convention X-Git-Url: https://git.stricted.de/?a=commitdiff_plain;h=3e5314d3c8364b3e3611256caa005bb34e05372e;p=GitHub%2FLineageOS%2Fandroid_kernel_motorola_exynos9610.git pwm: Document signal polarity convention The PWM subsystem defines normal and inversed PWM signal polarity in an unambiguous way. In addition to the documentation in the linux/pwm.h header file, add a paragraph in Documentation/pwm.txt because people are likely to look there for guidance. Signed-off-by: Thierry Reding --- diff --git a/Documentation/pwm.txt b/Documentation/pwm.txt index 93cb97974986..0527f615b115 100644 --- a/Documentation/pwm.txt +++ b/Documentation/pwm.txt @@ -97,6 +97,13 @@ pwm_chip as argument which provides a description of the PWM chip, the number of PWM devices provided by the chip and the chip-specific implementation of the supported PWM operations to the framework. +When implementing polarity support in a PWM driver, make sure to respect the +signal conventions in the PWM framework. By definition, normal polarity +characterizes a signal starts high for the duration of the duty cycle and +goes low for the remainder of the period. Conversely, a signal with inversed +polarity starts low for the duration of the duty cycle and goes high for the +remainder of the period. + Locking -------