On 12/02/2014 08:12 PM, Curt Brune wrote:
Hello,
I have a system where I need to change the "PWM invert" bit (bit 4) in
the PWM configuration register (offset 0x5C). The description of this
configuration bit from the data sheet:
This bit inverts the PWM output. The default is 0, which corresponds
to a logic high output for 100% duty cycle. Setting this bit to 1
inverts the PWM output, so 100% duty cycle corresponds to a logic
low output.
I noticed the adt7475.c driver does not expose this bit in sysfs.
Before hacking away I am curious to know why this configuration bit is
not exposed already. Some reasons I could think of:
- expect the power on default to be correct
- expect some other software (boot loader or BIOS) has already set it
- just never needed it
If it was just never needed then I am proposing to add 3 read/write
files to sysfs:
pwm1_invert
pwm2_invert
pwm3_invert
The values of 0 and 1 would have the same meaning as the "PWM invert"
bit (bit 4) in the PWM configuration register (offset 0x5C). Any
other value would be treated as -EINVAL.
This is usually a system attribute, not something to configure at
runtime. As such, expectation would be that it is set either with
platform data and/or with a devicetree property, not with a sysfs
attribute.
Guenter
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