Userspace interface breakage in power/state

Userspace interface breakage in power/state

[Matthew Garrett]

[-- Attachment #1: Type: text/plain, Size: 405 bytes --]

In older kernels, power/state for PCI devices took a PCI power state as 
an argument and so "3" was an entirely sensible thing to echo into it. 
In current kernels, it hits a BUG() in pci_choose_state and things blow 
up.

While I realise that the former interface was broken and wrong, would it 
be possible to move to a new one without breaking existing code? 
-- 
Matthew Garrett | mjg59@srcf.ucam.org

[-- Attachment #2: Type: text/plain, Size: 0 bytes --]

Userspace interface breakage in power/state

[Matthew Garrett]

[-- Attachment #1: Type: text/plain, Size: 494 bytes --]

(Resent, without the wrong address for lkml)

In older kernels, power/state for PCI devices took a PCI power state as 
an argument and so "3" was an entirely sensible thing to echo into it. 
In current kernels, it hits a BUG() in pci_choose_state and things blow 
up.

While I realise that the former interface was broken and wrong, would it 
be possible to move to a new one without breaking existing code? 
-- 
Matthew Garrett | mjg59@srcf.ucam.org

-- 
Matthew Garrett | mjg59@srcf.ucam.org

[-- Attachment #2: Type: text/plain, Size: 0 bytes --]

Re: Userspace interface breakage in power/state

[Pavel Machek]

[-- Attachment #1: Type: text/plain, Size: 541 bytes --]

On Po 16-01-06 00:25:17, Matthew Garrett wrote:
> In older kernels, power/state for PCI devices took a PCI power state as 
> an argument and so "3" was an entirely sensible thing to echo into it. 
> In current kernels, it hits a BUG() in pci_choose_state and things blow 
> up.
> 
> While I realise that the former interface was broken and wrong, would it 
> be possible to move to a new one without breaking existing code? 

I had patch to fix this breakage, but it was rejected. What depends on
that code?
								Pavel
-- 
Thanks, Sharp!

[-- Attachment #2: Type: text/plain, Size: 0 bytes --]

Re: Userspace interface breakage in power/state

[Matthew Garrett]

[-- Attachment #1: Type: text/plain, Size: 227 bytes --]

On Mon, Jan 16, 2006 at 08:20:36PM +0100, Pavel Machek wrote:

> I had patch to fix this breakage, but it was rejected. What depends on
> that code?

Ubuntu's wireless disable script.

-- 
Matthew Garrett | mjg59@srcf.ucam.org

[-- Attachment #2: Type: text/plain, Size: 0 bytes --]

Re: Userspace interface breakage in power/state

[Pavel Machek]

[-- Attachment #1: Type: text/plain, Size: 453 bytes --]

On Po 16-01-06 19:25:50, Matthew Garrett wrote:
> On Mon, Jan 16, 2006 at 08:20:36PM +0100, Pavel Machek wrote:
> 
> > I had patch to fix this breakage, but it was rejected. What depends on
> > that code?
> 
> Ubuntu's wireless disable script.

Can you search linux-pm archives? Search for "3" (that's '"', '3',
'"'). It should be somewhere. I no longer have a copy. (Probably could
get it from my working tree git...)

								Pavel
-- 
Thanks, Sharp!

[-- Attachment #2: Type: text/plain, Size: 0 bytes --]

Re: Userspace interface breakage in power/state

[Rafael J. Wysocki]

[-- Attachment #1: Type: text/plain, Size: 3720 bytes --]

Hi,

On Monday, 16 January 2006 21:05, Pavel Machek wrote:
> On Po 16-01-06 19:25:50, Matthew Garrett wrote:
> > On Mon, Jan 16, 2006 at 08:20:36PM +0100, Pavel Machek wrote:
> > 
> > > I had patch to fix this breakage, but it was rejected. What depends on
> > > that code?
> > 
> > Ubuntu's wireless disable script.
> 
> Can you search linux-pm archives? Search for "3" (that's '"', '3',
> '"'). It should be somewhere. I no longer have a copy. (Probably could
> get it from my working tree git...)

I think the appended message contains the latest version.

Greetings,
Rafael


----------  Forwarded Message  ----------

Subject: Re: [linux-pm] [patch] pm: fix runtime powermanagement's /sys interface
Date: Friday, 6 January 2006 00:08
From: Pavel Machek <pavel@ucw.cz>
To: Dominik Brodowski <linux@dominikbrodowski.net>, Patrick Mochel <mochel@digitalimplant.org>, Andrew Morton <akpm@osdl.org>, Linux-pm mailing list <linux-pm@lists.osdl.org>, kernel list <linux-kernel@vger.kernel.org>

On Čt 05-01-06 23:27:05, Dominik Brodowski wrote:
> On Thu, Jan 05, 2006 at 11:23:38PM +0100, Pavel Machek wrote:
> > > In addition, your patch breaks pcmcia / pcmciautils which already uses
> > > numbers (which I already had to change from "3" to "2" before...).
> > 
> > pcmcia actually uses this? Ouch. Do you just read the power file, or
> > do you write to it, too?
> 
> Reading and writing. Replacement for "cardctl suspend" and "cardctl resume".
> 
> 
> static int pccardctl_power_one(unsigned long socket_no, unsigned int device,
>                                unsigned int power)
> {
>         int ret;
>         char file[SYSFS_PATH_MAX];
>         struct sysfs_attribute *attr;
> 
>         snprintf(file, SYSFS_PATH_MAX,
>                  "/sys/bus/pcmcia/devices/%lu.%u/power/state",
>                  socket_no, device);
> 
>         attr = sysfs_open_attribute(file);
>         if (!attr)
>                 return -ENODEV;
> 
>         ret = sysfs_write_attribute(attr, power ? "2" : "0", 1);
> 
>         sysfs_close_attribute(attr);
> 
>         return (ret);
> }
> 
> 
> NB: it will break one day, one way or another, when gregkh makes the
> /sys/class -> /sys/devices conversion. However, I'd want to try not to break
> the new pcmciautils userspace too often...

Ok, so lets at least add value-checking to .../power file, and prevent
userspace see changes to PM_EVENT_SUSPEND value. 2 and 0 are now
"arbitrary cookies". I'd like to use "on" and "off", but pcmcia
apparently depends on "2" and "0", so...

Any objections?

Signed-off-by: Pavel Machek <pavel@suse.cz>
								Pavel

diff --git a/drivers/base/power/sysfs.c b/drivers/base/power/sysfs.c
--- a/drivers/base/power/sysfs.c
+++ b/drivers/base/power/sysfs.c
@@ -27,22 +27,25 @@
 
 static ssize_t state_show(struct device * dev, struct device_attribute *attr, char * buf)
 {
-	return sprintf(buf, "%u\n", dev->power.power_state.event);
+	if (dev->power.power_state.event)
+		return sprintf(buf, "2\n");
+	else
+		return sprintf(buf, "0\n");
 }
 
 static ssize_t state_store(struct device * dev, struct device_attribute *attr, const char * buf, size_t n)
 {
 	pm_message_t state;
-	char * rest;
-	int error = 0;
+	int error = -EINVAL;
 
-	state.event = simple_strtoul(buf, &rest, 10);
-	if (*rest)
-		return -EINVAL;
-	if (state.event)
-		error = dpm_runtime_suspend(dev, state);
-	else
+	state.event = PM_EVENT_SUSPEND;
+	if ((n == 1) && !strncmp(buf, "2", 1)) {
 		dpm_runtime_resume(dev);
+		error = 0;
+	}
+	if ((n == 1) && !strncmp(buf, "0", 1))
+		error = dpm_runtime_suspend(dev, state);
+
 	return error ? error : n;
 }
 


[-- Attachment #2: Type: text/plain, Size: 0 bytes --]

Re: Userspace interface breakage in power/state

[Pavel Machek]

[-- Attachment #1: Type: text/plain, Size: 2173 bytes --]

On Po 16-01-06 21:22:10, Rafael J. Wysocki wrote:
> Hi,
> 
> On Monday, 16 January 2006 21:05, Pavel Machek wrote:
> > On Po 16-01-06 19:25:50, Matthew Garrett wrote:
> > > On Mon, Jan 16, 2006 at 08:20:36PM +0100, Pavel Machek wrote:
> > > 
> > > > I had patch to fix this breakage, but it was rejected. What depends on
> > > > that code?
> > > 
> > > Ubuntu's wireless disable script.
> > 
> > Can you search linux-pm archives? Search for "3" (that's '"', '3',
> > '"'). It should be somewhere. I no longer have a copy. (Probably could
> > get it from my working tree git...)
> 
> I think the appended message contains the latest version.

Thanks, thats it. Matthew, you probably want to replace "2" with "3"
below.

								Pavel

> Ok, so lets at least add value-checking to .../power file, and prevent
> userspace see changes to PM_EVENT_SUSPEND value. 2 and 0 are now
> "arbitrary cookies". I'd like to use "on" and "off", but pcmcia
> apparently depends on "2" and "0", so...
> 
> Any objections?
> 
> Signed-off-by: Pavel Machek <pavel@suse.cz>
> 								Pavel
> 
> diff --git a/drivers/base/power/sysfs.c b/drivers/base/power/sysfs.c
> --- a/drivers/base/power/sysfs.c
> +++ b/drivers/base/power/sysfs.c
> @@ -27,22 +27,25 @@
>  
>  static ssize_t state_show(struct device * dev, struct device_attribute *attr, char * buf)
>  {
> -	return sprintf(buf, "%u\n", dev->power.power_state.event);
> +	if (dev->power.power_state.event)
> +		return sprintf(buf, "2\n");
> +	else
> +		return sprintf(buf, "0\n");
>  }
>  
>  static ssize_t state_store(struct device * dev, struct device_attribute *attr, const char * buf, size_t n)
>  {
>  	pm_message_t state;
> -	char * rest;
> -	int error = 0;
> +	int error = -EINVAL;
>  
> -	state.event = simple_strtoul(buf, &rest, 10);
> -	if (*rest)
> -		return -EINVAL;
> -	if (state.event)
> -		error = dpm_runtime_suspend(dev, state);
> -	else
> +	state.event = PM_EVENT_SUSPEND;
> +	if ((n == 1) && !strncmp(buf, "2", 1)) {
>  		dpm_runtime_resume(dev);
> +		error = 0;
> +	}
> +	if ((n == 1) && !strncmp(buf, "0", 1))
> +		error = dpm_runtime_suspend(dev, state);
> +
>  	return error ? error : n;
>  }
>  

-- 
Thanks, Sharp!

[-- Attachment #2: Type: text/plain, Size: 0 bytes --]