diff options
Diffstat (limited to 'Documentation/pwm.txt')
| -rw-r--r-- | Documentation/pwm.txt | 14 |
1 files changed, 11 insertions, 3 deletions
diff --git a/Documentation/pwm.txt b/Documentation/pwm.txt index 1039b68fe9c..ca895fd211e 100644 --- a/Documentation/pwm.txt +++ b/Documentation/pwm.txt @@ -19,7 +19,8 @@ should instead register a static mapping that can be used to match PWM consumers to providers, as given in the following example: static struct pwm_lookup board_pwm_lookup[] = { - PWM_LOOKUP("tegra-pwm", 0, "pwm-backlight", NULL), + PWM_LOOKUP("tegra-pwm", 0, "pwm-backlight", NULL, + 50000, PWM_POLARITY_NORMAL), }; static void __init board_init(void) @@ -39,7 +40,7 @@ New users should use the pwm_get() function and pass to it the consumer device or a consumer name. pwm_put() is used to free the PWM device. Managed variants of these functions, devm_pwm_get() and devm_pwm_put(), also exist. -After being requested a PWM has to be configured using: +After being requested, a PWM has to be configured using: int pwm_config(struct pwm_device *pwm, int duty_ns, int period_ns); @@ -94,9 +95,16 @@ for new drivers to use the generic PWM framework. A new PWM controller/chip can be added using pwmchip_add() and removed again with pwmchip_remove(). pwmchip_add() takes a filled in struct pwm_chip as argument which provides a description of the PWM chip, the -number of PWM devices provider by the chip and the chip-specific +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 ------- |