[PATCH] sbs-battery: probe should try talking to the device

[Olof Johansson <olof@lixom.net>]

Turns out this driver doesn't actually try talking to the device at
probe time, so if it's incorrectly configured in the device tree or
platform data (or if the battery has been removed from the system), then
probe will succeed and every access will sit there and time out. The
end result is a possibly laggy system that thinks it has a battery but
can never read status, which isn't very useful.

Instead, just read any register (I chose status) at probe, and if that
fails, don't register the device.

Signed-off-by: Olof Johansson <olof@lixom.net>
---
 drivers/power/sbs-battery.c | 10 ++++++++++
 1 file changed, 10 insertions(+)

diff --git a/drivers/power/sbs-battery.c b/drivers/power/sbs-battery.c
index a65e8f5..2f24253 100644
--- a/drivers/power/sbs-battery.c
+++ b/drivers/power/sbs-battery.c
@@ -760,6 +760,16 @@ static int __devinit sbs_probe(struct i2c_client *client,
 
 skip_gpio:
 
+	/* Before we register, we need to make sure we can actually talk
+	 * to the battery.
+	 */
+	rc = sbs_read_word_data(client, sbs_data[REG_STATUS].addr);
+	if (rc < 0) {
+		dev_err(&client->dev, "%s: Failed to get device status\n",
+			__func__);
+		goto exit_psupply;
+	}
+
 	rc = power_supply_register(&client->dev, &chip->power_supply);
 	if (rc) {
 		dev_err(&client->dev,
-- 
1.7.10.1.488.g05fbf7a