rtc: add dm_rtc_read helper and ->read method

Some users may want to read multiple consecutive 8-bit
registers. Instead of each caller having to implement the loop,
provide a dm_rtc_read() helper. Also, allow a driver to provide a
->read method, which can be more efficient than reading one register
at a time.

Reviewed-by: Simon Glass <sjg@chromium.org>
Reviewed-by: Heiko Schocher <hs@denx.de>
Signed-off-by: Rasmus Villemoes <rasmus.villemoes@prevas.dk>

1 files changed, 19 insertions, 0 deletions

diff --git a/drivers/rtc/rtc-uclass.c b/drivers/rtc/rtc-uclass.c
index 926cca2..4a0e3c5 100644
--- a/drivers/rtc/rtc-uclass.c
+++ b/drivers/rtc/rtc-uclass.c
@@ -40,6 +40,25 @@ int dm_rtc_reset(struct udevice *dev)
 	return ops->reset(dev);
 }
 
+int dm_rtc_read(struct udevice *dev, unsigned int reg, u8 *buf, unsigned int len)
+{
+	struct rtc_ops *ops = rtc_get_ops(dev);
+
+	assert(ops);
+	if (ops->read)
+		return ops->read(dev, reg, buf, len);
+	if (!ops->read8)
+		return -ENOSYS;
+	while (len--) {
+		int ret = ops->read8(dev, reg++);
+
+		if (ret < 0)
+			return ret;
+		*buf++ = ret;
+	}
+	return 0;
+}
+
 int rtc_read8(struct udevice *dev, unsigned int reg)
 {
 	struct rtc_ops *ops = rtc_get_ops(dev);