forked from luck/tmp_suning_uos_patched
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>
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@ -97,6 +97,13 @@ pwm_chip as argument which provides a description of the PWM chip, the
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number of PWM devices provided by the chip and the chip-specific
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implementation of the supported PWM operations to the framework.
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When implementing polarity support in a PWM driver, make sure to respect the
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signal conventions in the PWM framework. By definition, normal polarity
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characterizes a signal starts high for the duration of the duty cycle and
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goes low for the remainder of the period. Conversely, a signal with inversed
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polarity starts low for the duration of the duty cycle and goes high for the
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remainder of the period.
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Locking
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