[PATCH v3] rtc-pcf8523: Add low battery voltage support

[Jesper Nilsson]

This patch implements reading of the battery voltage low signal for
rtc-pcf8523.

The bit is read-only and cannot be cleared by software, so no
clear-function is implemented.

Signed-off-by: Jesper Nilsson <jesper.nilsson@xxxxxxxx>
Reviewed-by: Thierry Reding <thierry.reding@xxxxxxxxxxxxxxxxx>
---
diff --git a/drivers/rtc/rtc-pcf8523.c b/drivers/rtc/rtc-pcf8523.c
index be05a64..acede49 100644
--- a/drivers/rtc/rtc-pcf8523.c
+++ b/drivers/rtc/rtc-pcf8523.c
@@ -23,6 +23,7 @@
 #define REG_CONTROL3_PM_VDD (1 << 6) /* switch-over disabled */
 #define REG_CONTROL3_PM_DSM (1 << 5) /* direct switching mode */
 #define REG_CONTROL3_PM_MASK 0xe0
+#define REG_CONTROL3_BLF (1 << 2) /* battery low bit, read-only */
 
 #define REG_SECONDS  0x03
 #define REG_SECONDS_OS (1 << 7)
@@ -250,9 +252,35 @@ static int pcf8523_rtc_set_time(struct device *dev, struct rtc_time *tm)
 	return pcf8523_start_rtc(client);
 }
 
+static int pcf8523_rtc_ioctl(struct device *dev, unsigned int cmd,
+			     unsigned long arg)
+{
+	struct i2c_client *client = to_i2c_client(dev);
+	u8 value;
+	int ret = 0, err;
+
+	switch (cmd) {
+	case RTC_VL_READ:
+		err = pcf8523_read(client, REG_CONTROL3, &value);
+		if (err < 0)
+			return err;
+
+		if (value & REG_CONTROL3_BLF)
+			ret = 1;
+
+		if (copy_to_user((void __user *)arg, &ret, sizeof(int)))
+			return -EFAULT;
+
+		return 0;
+	default:
+		return -ENOIOCTLCMD;
+	}
+}
+
 static const struct rtc_class_ops pcf8523_rtc_ops = {
 	.read_time = pcf8523_rtc_read_time,
 	.set_time = pcf8523_rtc_set_time,
+	.ioctl = pcf8523_rtc_ioctl,
 };
 
 static int pcf8523_probe(struct i2c_client *client,

/^JN - Jesper Nilsson
-- 
               Jesper Nilsson -- jesper.nilsson@xxxxxxxx
--
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