[PATCH] preserve correct battery state through suspend/resume cycles

[Jiri Kosina]

There is a problem in th following scenario(s):

boot -> suspend -> (un)plug battery -> resume

The problem arises in both cases - i.e. suspend with battery plugged in, 
and resume with battery unplugged, or vice versa.

After resume, when the battery status has changed (plugged in -> unplegged 
or unplugged -> plugged in) during the time when the system was sleeping, 
the /proc/acpi/battery/*/* is wrong (showing the state before suspend, not 
the current state).

The following patch adds ->resume method to the ACPI battery handler, which
has the only aim - to check whether the battery state has changed during sleep, 
and if so, update the ACPI internal data structures, so that information 
published through /proc/acpi/battery/*/* is correct even after suspend/resume
cycle, during which the battery was removed/inserted.

The patch is against current ACPI git tree, but applies cleanly also 
against -mm and probably other trees. Please apply.

Signed-off-by: Jiri Kosina <jikos@xxxxxxxx>

 drivers/acpi/battery.c |   15 +++++++++++++++
 1 files changed, 15 insertions(+), 0 deletions(-)

diff --git a/drivers/acpi/battery.c b/drivers/acpi/battery.c
index 9810e2a..82a0f5b 100644
--- a/drivers/acpi/battery.c
+++ b/drivers/acpi/battery.c
@@ -64,6 +64,7 @@ extern void *acpi_unlock_battery_dir(str
 
 static int acpi_battery_add(struct acpi_device *device);
 static int acpi_battery_remove(struct acpi_device *device, int type);
+static int acpi_battery_resume(struct acpi_device *device, int status);
 
 static struct acpi_driver acpi_battery_driver = {
 	.name = ACPI_BATTERY_DRIVER_NAME,
@@ -71,6 +72,7 @@ static struct acpi_driver acpi_battery_d
 	.ids = ACPI_BATTERY_HID,
 	.ops = {
 		.add = acpi_battery_add,
+		.resume = acpi_battery_resume,
 		.remove = acpi_battery_remove,
 		},
 };
@@ -753,6 +755,19 @@ static int acpi_battery_remove(struct ac
 	return 0;
 }
 
+/* this is needed to learn about changes made in suspended state */
+static int acpi_battery_resume(struct acpi_device *device, int state)
+{
+	struct acpi_battery *battery;
+	
+	if (!device)
+		return -EINVAL;
+	
+	battery = (struct acpi_battery *)device->driver_data;
+	return acpi_battery_check(battery);
+	
+}
+
 static int __init acpi_battery_init(void)
 {
 	int result;

-- 
Jiri Kosina
-
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