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| author | Thierry Reding <thierry.reding@gmail.com> | 2014-04-07 15:45:30 +0200 |
|---|---|---|
| committer | Thierry Reding <thierry.reding@gmail.com> | 2014-04-28 13:04:59 +0200 |
| commit | 3e5314d3c8364b3e3611256caa005bb34e05372e (patch) | |
| tree | ee7cf0715d4c6053f3f66280ff8a60038b05a3b5 | |
| parent | Linux 3.15-rc1 (diff) | |
| download | linux-3e5314d3c8364b3e3611256caa005bb34e05372e.tar.xz linux-3e5314d3c8364b3e3611256caa005bb34e05372e.zip | |
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 <thierry.reding@gmail.com>
| -rw-r--r-- | Documentation/pwm.txt | 7 |
1 files changed, 7 insertions, 0 deletions
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 ------- |