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Kernel driver pwm-fan
This driver enables the use of a PWM module to drive a fan. It uses the
generic PWM interface thus it is hardware independent. It can be used on
many SoCs, as long as the SoC supplies a PWM line driver that exposes
the generic PWM API.
Author: Kamil Debski <>
The driver implements a simple interface for driving a fan connected to
a PWM output. It uses the generic PWM interface, thus it can be used with
a range of SoCs. The driver exposes the fan to the user space through
the hwmon's sysfs interface.
The fan rotation speed returned via the optional 'fan1_input' is extrapolated
from the sampled interrupts from the tachometer signal within 1 second.
The driver provides the following sensor accesses in sysfs:
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fan1_input ro fan tachometer speed in RPM
pwm1_enable rw keep enable mode, defines behaviour when pwm1=0
0 -> disable pwm and regulator
1 -> enable pwm; if pwm==0, disable pwm, keep regulator enabled
2 -> enable pwm; if pwm==0, keep pwm and regulator enabled
3 -> enable pwm; if pwm==0, disable pwm and regulator
pwm1 rw relative speed (0-255), 255=max. speed.
=============== ======= =======================================================