linux-kernel - [PATCH 1/1] battery: only refresh the sysfs files when pertinant information changes

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Date:	Thu,  3 May 2012 14:48:26 +0100
From:	Andy Whitcroft <apw@...onical.com>
To:	Matthew Garrett <mjg59@...f.ucam.org>,
	"Rafael J. Wysocki" <rjw@...k.pl>,
	Jonathan Nieder <jrnieder@...il.com>
Cc:	Andy Whitcroft <apw@...onical.com>,
	ACPI Devel Maling List <linux-acpi@...r.kernel.org>,
	Linux-pm mailing list <linux-pm@...ts.linux-foundation.org>,
	Adrian Fita <adrian.fita@...il.com>,
	Len Brown <lenb@...nel.org>, Ralf Jung <ralfjung-e@....de>,
	Paolo Scarabelli <paolo@....it>, linux-kernel@...r.kernel.org
Subject: [PATCH 1/1] battery: only refresh the sysfs files when pertinant information changes

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

Signed-off-by: Andy Whitcroft <apw@...onical.com>
---
 drivers/acpi/battery.c |   10 +++++++++-
 1 file changed, 9 insertions(+), 1 deletion(-)

	Based on Matthew's feedback here is a version which optimises
	based on the power_unit field as returned from the battery info.
	Could someone who suffers from this issue please test this out
	and report back.  Thanks.

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);
 }
-- 
1.7.9.5

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