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.

[akpm@linux-foundation.org: omit pcf8563_rtc_ioctl() if CONFIG_RTC_INTF_DEV=n]
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>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 31 insertions, 0 deletions

diff --git a/drivers/rtc/rtc-pcf8523.c b/drivers/rtc/rtc-pcf8523.c
index be05a645f99e..889e3160e701 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 +251,39 @@ static int pcf8523_rtc_set_time(struct device *dev, struct rtc_time *tm)
         return pcf8523_start_rtc(client);
 }
 
+#ifdef CONFIG_RTC_INTF_DEV
+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;
+        }
+}
+#else
+#define pcf8523_rtc_ioctl NULL
+#endif
+
 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,