[PATCH 2/4] [pm] Respect the real device power states in sysfs interface

[Patrick Mochel <mochel@digitalimplant.org>]

On read, the actual state the device is in is reported (as
recorded in the pm_message_t::state field), instead of just
"0" or "2" (which roughly map to "on" and "off"). If the
device is suspended, but the state is "0", then report
PM_STATE_OFF (defined as INT_MAX).

On write, pass the value that the user wrote to the device/
bus suspend method (via the pm_message_t::state field), so
that the device can enter the state specified by the user
process.

This retains the semantics of treating any non-zero state
request as a suspend request, setting the /event field to
PM_EVENT_SUSPEND. A value of 0 gets an .event field set to
PM_EVENT_ON.

Previously, the file interface was changed to filter all
values except "0", "2", and "3". This patch removes that
artificial filtering to let the bus/device drivers decide
what values are relevant for them, and returns the file to
its originally designed interface - to allow a user process
to place a device in the specified state.

Signed-off-by: Patrick Mochel <mochel@linux.intel.com>

---

 drivers/base/power/sysfs.c |   66 ++++++++++++++++++++++++++------------------
 1 files changed, 39 insertions(+), 27 deletions(-)

applies-to: 11a0502281f83482175ce71b583059b04cdef8ad
791cab449feafe0e35a7345502c2d2e26dc51d88
diff --git a/drivers/base/power/sysfs.c b/drivers/base/power/sysfs.c
index 40d7242..308baff 100644
--- a/drivers/base/power/sysfs.c
+++ b/drivers/base/power/sysfs.c
@@ -7,50 +7,62 @@
 #include "power.h"


+#define PM_STATE_OFF	INT_MAX
+
 /**
  *	state - Control current power state of device
  *
  *	show() returns the current power state of the device. '0' indicates
  *	the device is on. Other values (1-3) indicate the device is in a low
  *	power state.
- *
- *	store() sets the current power state, which is an integer value
- *	between 0-3. If the device is on ('0'), and the value written is
- *	greater than 0, then the device is placed directly into the low-power
- *	state (via its driver's ->suspend() method).
- *	If the device is currently in a low-power state, and the value is 0,
- *	the device is powered back on (via the ->resume() method).
- *	If the device is in a low-power state, and a different low-power state
- *	is requested, the device is first resumed, then suspended into the new
- *	low-power state.
+ *	A value of INT_MAX (0x0fffffff) indicates that the device is off - it is
+ *	suspended, but the actual state is unknown (for devices and buses that only
+ *	support "on" and "off").
+ *
+ *	store() takes an integer value and changes the current power state of the
+ *	device. If this value is 0, the device is resumed - a PM message with event
+ *	type PM_EVENT_ON, and a state of 0 is passed to dpm_runtime_resume().
+ *	Otherwise, the device is suspended. A PM message with event type
+ *	PM_EVENT_SUSPEND is passed to the device, with the state being the value
+ *	written to this file.
+ *
+ *	The meaning of the integer value states are bus and/or device specific, with
+ *	the exception of 0 - that always means "on".
+ *	The core will not do any further interpretation of the values. It is up to
+ *	the bus and/or device drivers to both document and check the values that are
+ *	read and written from this file.
+ *	For buses and devices that only support "on" and "off", any non-zero number
+ *	can be used to indicate "off".
  */

 static ssize_t state_show(struct device * dev, struct device_attribute *attr, char * buf)
 {
-	if (dev->power.power_state.event)
-		return sprintf(buf, "2\n");
-	else
-		return sprintf(buf, "0\n");
+	u32 state = 0;
+
+	if (dev->power.power_state.event == PM_EVENT_SUSPEND) {
+		state = dev->power.power_state.state;
+		if (!state)
+			state = PM_STATE_OFF;
+	}
+	return sprintf(buf, "%x\n", dev->power.power_state.state);
 }

 static ssize_t state_store(struct device * dev, struct device_attribute *attr, const char * buf, size_t n)
 {
-	pm_message_t state;
-	int error = -EINVAL;
+	pm_message_t msg = {
+		.event = PM_EVENT_SUSPEND,
+	};
+	char * rest;
+	int error = 0;

-	state.event = PM_EVENT_SUSPEND;
-	/* Older apps expected to write "3" here - confused with PCI D3 */
-	if ((n == 1) && !strcmp(buf, "3"))
-		error = dpm_runtime_suspend(dev, state);
-
-	if ((n == 1) && !strcmp(buf, "2"))
-		error = dpm_runtime_suspend(dev, state);
+	msg.state = simple_strtoul(buf, &rest, 0);
+	if (*rest)
+		return -EINVAL;

-	if ((n == 1) && !strcmp(buf, "0")) {
+	if (msg.state)
+		error = dpm_runtime_suspend(dev, msg);
+	else
 		dpm_runtime_resume(dev);
-		error = 0;
-	}
-
 	return error ? error : n;
 }

---
0.99.9.GIT
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