linux-kernel - [PATCH 01/15] ACPI battery: only refresh the sysfs files when pertinent information changes

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Date:	Mon,  4 Jun 2012 01:39:52 -0400
From:	Len Brown <lenb@...nel.org>
To:	linux-acpi@...r.kernel.org, linux-pm@...ts.linux-foundation.org
Cc:	linux-kernel@...r.kernel.org, Andy Whitcroft <apw@...onical.com>,
	<stable@...r.kernel.org>, Len Brown <len.brown@...el.com>
Subject: [PATCH 01/15] ACPI battery: only refresh the sysfs files when pertinent information changes

From: Andy Whitcroft <apw@...onical.com>

We only need to regenerate the sysfs files when the capacity units
change, avoid the update otherwise.

The origin of this issue is dates way back to 2.6.38:
da8aeb92d4853f37e281f11fddf61f9c7d84c3cd
(ACPI / Battery: Update information on info notification and resume)

cc: <stable@...r.kernel.org>
Signed-off-by: Andy Whitcroft <apw@...onical.com>
Tested-by: Ralf Jung <post@...fj.de>
Signed-off-by: Len Brown <len.brown@...el.com>
---
 drivers/acpi/battery.c | 10 +++++++++-
 1 file changed, 9 insertions(+), 1 deletion(-)

diff --git a/drivers/acpi/battery.c b/drivers/acpi/battery.c
index 86933ca..7dd3f9f 100644
--- a/drivers/acpi/battery.c
+++ b/drivers/acpi/battery.c
@@ -643,11 +643,19 @@ static int acpi_battery_update(struct acpi_battery *battery)
 
 static void acpi_battery_refresh(struct acpi_battery *battery)
 {
+	int power_unit;
+
 	if (!battery->bat.dev)
 		return;
 
+	power_unit = battery->power_unit;
+
 	acpi_battery_get_info(battery);
-	/* The battery may have changed its reporting units. */
+
+	if (power_unit == battery->power_unit)
+		return;
+
+	/* The battery has changed its reporting units. */
 	sysfs_remove_battery(battery);
 	sysfs_add_battery(battery);
 }
-- 
1.7.11.rc0.100.g5498c5f

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