Re: Userspace interface breakage in power/state

["Rafael J. Wysocki" <rjw@sisk.pl>]

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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;
 }
 


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