rtc-pcf8523: add low battery voltage support

Implement 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@axis.com>
Reviewed-by: Thierry Reding <thierry.reding@avionic-design.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

diff --git a/drivers/rtc/rtc-pcf8523.c b/drivers/rtc/rtc-pcf8523.c
index be05a645f99e985ebea76a9a9903ffdead17fb4c..0696ab2b7c57640b6e052745886b771e0ae6b333 100644 (file)
--- 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 +251,35 @@ 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,