apm for individual devices

apm for individual devices

[Tehn Yit Chin]

Hi all,

How does one use the sysfs entry of power/state that I can find for each 
registered device? Eg, for the i2c device on my s3c2410 cpu, I find the 
following entry,

/sys/devices/platform/s3c2410-i2c/power/state

I tried echoing "mem" into it, but nothing seems to happen.

What I am looking for is a way of suspending and resuming individual 
devices within the PM architecture?

Any pointers would be greatly appreciated.
-- 
Tehn Yit Chin
Software Engineer, Grey Innovation Pty. Ltd.

Re: apm for individual devices

[Tehn Yit Chin]

Tehn Yit Chin wrote:
> Hi all,
> 
> How does one use the sysfs entry of power/state that I can find for each 
> registered device? Eg, for the i2c device on my s3c2410 cpu, I find the 
> following entry,
> 
> /sys/devices/platform/s3c2410-i2c/power/state
> 
> I tried echoing "mem" into it, but nothing seems to happen.
> 
> What I am looking for is a way of suspending and resuming individual 
> devices within the PM architecture?
> 
> Any pointers would be greatly appreciated.

After reading through the mailing list archives, I sort of work it out. ie

echo -n 1 > /sys/devices/platform/s3c2410-i2c/power/state

puts the device into suspend mode.

However, the driver's behaviour doesn't change if I echo a different 
number into it. What does this number suppose to do?

Tehn Yit Chin
Software Engineer, Grey Innovation Pty. Ltd.

Re: apm for individual devices

[Patrick Mochel]

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On Tue, 7 Mar 2006, Tehn Yit Chin wrote:

> After reading through the mailing list archives, I sort of work it out. ie
>
> echo -n 1 > /sys/devices/platform/s3c2410-i2c/power/state
>
> puts the device into suspend mode.
>
> However, the driver's behaviour doesn't change if I echo a different
> number into it. What does this number suppose to do?

It depends on how the i2c subsystem (and possibly the driver) treats the
number. It might have only 2 states - on (0) and off (1). But, you'll have
to check the i2c documentation, the code, and possibly the developers to
know for sure..

Thanks,


	Patrick

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Re: apm for individual devices

[Pavel Machek]

On Út 07-03-06 12:30:22, Tehn Yit Chin wrote:
> 
> Tehn Yit Chin wrote:
> >Hi all,
> >
> >How does one use the sysfs entry of power/state that I can find for each 
> >registered device? Eg, for the i2c device on my s3c2410 cpu, I find the 
> >following entry,
> >
> >/sys/devices/platform/s3c2410-i2c/power/state
> >
> >I tried echoing "mem" into it, but nothing seems to happen.
> >
> >What I am looking for is a way of suspending and resuming individual 
> >devices within the PM architecture?
> >
> >Any pointers would be greatly appreciated.
> 
> After reading through the mailing list archives, I sort of work it out. ie
> 
> echo -n 1 > /sys/devices/platform/s3c2410-i2c/power/state

Actually, it is controlled by 0 and 3 these days. (0 == on, 3 == off).

								Pavel
-- 
Web maintainer for suspend.sf.net (www.sf.net/projects/suspend) wanted...

Re: apm for individual devices

[Adam Belay]

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On Tue, Mar 07, 2006 at 11:44:35AM +1100, Tehn Yit Chin wrote:
> Hi all,
> 
> How does one use the sysfs entry of power/state that I can find for each 
> registered device? Eg, for the i2c device on my s3c2410 cpu, I find the 
> following entry,
> 
> /sys/devices/platform/s3c2410-i2c/power/state
> 
> I tried echoing "mem" into it, but nothing seems to happen.
> 
> What I am looking for is a way of suspending and resuming individual 
> devices within the PM architecture?
> 
> Any pointers would be greatly appreciated.
> --

Out of curiousity, why do you need to suspend this individual device?
In other words, what practical runtime power management gains would this
sort of low level and specific power management control provide for your
purposes?

Thanks,
Adam


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Re: apm for individual devices

[Tehn Yit Chin]

Adam Belay wrote:
> On Tue, Mar 07, 2006 at 11:44:35AM +1100, Tehn Yit Chin wrote:
> 
>>Hi all,
>>
>>How does one use the sysfs entry of power/state that I can find for each 
>>registered device? Eg, for the i2c device on my s3c2410 cpu, I find the 
>>following entry,
>>
>>/sys/devices/platform/s3c2410-i2c/power/state
>>
>>I tried echoing "mem" into it, but nothing seems to happen.
>>
>>What I am looking for is a way of suspending and resuming individual 
>>devices within the PM architecture?
>>
>>Any pointers would be greatly appreciated.
>>--
> 
> 
> Out of curiousity, why do you need to suspend this individual device?
> In other words, what practical runtime power management gains would this
> sort of low level and specific power management control provide for your
> purposes?
> 
> Thanks,
> Adam
> 
> 

The example that I use is probably a bad example.

We are developing a  consumer electronic product where we need to shut 
down various devices in the product's several operating mode to maximise 
battery life. Eg: in one of its operating mode, we are not using the 
audio codec so we should suspend it to maximise battery life. There are 
also several similar scenarios where this could apply.

A better example might have been

echo -n 1 > /dev/devices/platform/product-codec/power/state

cheers,
tyc

RE: apm for individual devices

[Li Qiang-E3422C]

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'0' indicates the device is on. Other values (1-3) indicate the device
is in a low power state. 
You can see ACPI's spec.

-----Original Message-----
From: linux-pm-bounces@lists.osdl.org
[mailto:linux-pm-bounces@lists.osdl.org] On Behalf Of Tehn Yit Chin
Sent: Tuesday, March 07, 2006 9:30 AM
To: Tehn Yit Chin
Cc: linux-pm@lists.osdl.org
Subject: Re: [linux-pm] apm for individual devices


Tehn Yit Chin wrote:
> Hi all,
> 
> How does one use the sysfs entry of power/state that I can find for 
> each registered device? Eg, for the i2c device on my s3c2410 cpu, I 
> find the following entry,
> 
> /sys/devices/platform/s3c2410-i2c/power/state
> 
> I tried echoing "mem" into it, but nothing seems to happen.
> 
> What I am looking for is a way of suspending and resuming individual 
> devices within the PM architecture?
> 
> Any pointers would be greatly appreciated.

After reading through the mailing list archives, I sort of work it out.
ie

echo -n 1 > /sys/devices/platform/s3c2410-i2c/power/state

puts the device into suspend mode.

However, the driver's behaviour doesn't change if I echo a different
number into it. What does this number suppose to do?

Tehn Yit Chin
Software Engineer, Grey Innovation Pty. Ltd.

_______________________________________________
linux-pm mailing list
linux-pm@lists.osdl.org
https://lists.osdl.org/mailman/listinfo/linux-pm


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Re: apm for individual devices

[Pavel Machek]

On Út 07-03-06 10:11:31, Li Qiang-E3422C wrote:
> '0' indicates the device is on. Other values (1-3) indicate the device
> is in a low power state. 
> You can see ACPI's spec.

Actually, no. This is broken interface, please do not use it. 0 == on,
2 or 3 == off. But do not use it.
								Pavel
-- 
Web maintainer for suspend.sf.net (www.sf.net/projects/suspend) wanted...

Re: apm for individual devices

[Tehn Yit Chin]

Pavel Machek wrote:
> On Út 07-03-06 10:11:31, Li Qiang-E3422C wrote:
> 
>>'0' indicates the device is on. Other values (1-3) indicate the device
>>is in a low power state. 
>>You can see ACPI's spec.
> 
> 
> Actually, no. This is broken interface, please do not use it. 0 == on,
> 2 or 3 == off. But do not use it.
> 								Pavel

Are you saying not to the the power/state that is present in the 
device's sysfs entry? What interface do you recommend that I use?

cheers,
tyc

Re: apm for individual devices

[Pavel Machek]

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On Čt 09-03-06 12:57:42, Tehn Yit Chin wrote:
> Pavel Machek wrote:
> >On Út 07-03-06 10:11:31, Li Qiang-E3422C wrote:
> >
> >>'0' indicates the device is on. Other values (1-3) indicate the device
> >>is in a low power state. 
> >>You can see ACPI's spec.
> >
> >
> >Actually, no. This is broken interface, please do not use it. 0 == on,
> >2 or 3 == off. But do not use it.
> 
> Are you saying not to the the power/state that is present in the 
> device's sysfs entry? What interface do you recommend that I use?

Parse error. But I'm trying to say that <device>/power/state should
not be used -- it is ugly/broken. Replacement interface is being
prepared by Patrick, I believe, but is not yet in mainline. Feel free
to help Patrick :-).

								Pavel
-- 
Web maintainer for suspend.sf.net (www.sf.net/projects/suspend) wanted...

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