* [lm-sensors] adt7475 driver: PWM invert configuration bit
@ 2014-12-03 4:12 Curt Brune
2014-12-03 5:29 ` Guenter Roeck
` (2 more replies)
0 siblings, 3 replies; 4+ messages in thread
From: Curt Brune @ 2014-12-03 4:12 UTC (permalink / raw)
To: lm-sensors
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.
Cheers,
Curt
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^ permalink raw reply [flat|nested] 4+ messages in thread
* Re: [lm-sensors] adt7475 driver: PWM invert configuration bit
2014-12-03 4:12 [lm-sensors] adt7475 driver: PWM invert configuration bit Curt Brune
@ 2014-12-03 5:29 ` Guenter Roeck
2014-12-04 0:18 ` Curt Brune
2014-12-04 1:10 ` Guenter Roeck
2 siblings, 0 replies; 4+ messages in thread
From: Guenter Roeck @ 2014-12-03 5:29 UTC (permalink / raw)
To: lm-sensors
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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^ permalink raw reply [flat|nested] 4+ messages in thread
* Re: [lm-sensors] adt7475 driver: PWM invert configuration bit
2014-12-03 4:12 [lm-sensors] adt7475 driver: PWM invert configuration bit Curt Brune
2014-12-03 5:29 ` Guenter Roeck
@ 2014-12-04 0:18 ` Curt Brune
2014-12-04 1:10 ` Guenter Roeck
2 siblings, 0 replies; 4+ messages in thread
From: Curt Brune @ 2014-12-04 0:18 UTC (permalink / raw)
To: lm-sensors
Hello Guenter,
On Tue Dec 02 21:29, Guenter Roeck wrote:
>
> 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.
>
Thanks for the input. I will consider the platform data and/or
devicetree property approach.
Cheers,
Curt
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^ permalink raw reply [flat|nested] 4+ messages in thread
* Re: [lm-sensors] adt7475 driver: PWM invert configuration bit
2014-12-03 4:12 [lm-sensors] adt7475 driver: PWM invert configuration bit Curt Brune
2014-12-03 5:29 ` Guenter Roeck
2014-12-04 0:18 ` Curt Brune
@ 2014-12-04 1:10 ` Guenter Roeck
2 siblings, 0 replies; 4+ messages in thread
From: Guenter Roeck @ 2014-12-04 1:10 UTC (permalink / raw)
To: lm-sensors
On Wed, Dec 03, 2014 at 04:18:45PM -0800, Curt Brune wrote:
> Hello Guenter,
>
> On Tue Dec 02 21:29, Guenter Roeck wrote:
> >
> > 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.
> >
>
> Thanks for the input. I will consider the platform data and/or
> devicetree property approach.
>
Hi Curt,
Patches are welcome ...
Thanks,
Guenter
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^ permalink raw reply [flat|nested] 4+ messages in thread
end of thread, other threads:[~2014-12-04 1:10 UTC | newest]
Thread overview: 4+ messages (download: mbox.gz / follow: Atom feed)
-- links below jump to the message on this page --
2014-12-03 4:12 [lm-sensors] adt7475 driver: PWM invert configuration bit Curt Brune
2014-12-03 5:29 ` Guenter Roeck
2014-12-04 0:18 ` Curt Brune
2014-12-04 1:10 ` Guenter Roeck
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