[PATCH v2 01/10] rtc: add rtc_read helper and ->read method

[Rasmus Villemoes]

Some users may want to read multiple consecutive 8-bit
registers. Instead of each caller having to implement the loop,
provide a 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 <s...@chromium.org>
Signed-off-by: Rasmus Villemoes <rasmus.villem...@prevas.dk>
---
 drivers/rtc/rtc-uclass.c | 18 ++++++++++++++++++
 include/rtc.h            | 23 +++++++++++++++++++++++
 2 files changed, 41 insertions(+)

diff --git a/drivers/rtc/rtc-uclass.c b/drivers/rtc/rtc-uclass.c
index a0a238aedd..44d76bb70f 100644
--- a/drivers/rtc/rtc-uclass.c
+++ b/drivers/rtc/rtc-uclass.c
@@ -39,6 +39,24 @@ int dm_rtc_reset(struct udevice *dev)
        return ops->reset(dev);
 }
 
+int 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);
diff --git a/include/rtc.h b/include/rtc.h
index 8aabfc1162..1c9c09fef8 100644
--- a/include/rtc.h
+++ b/include/rtc.h
@@ -55,6 +55,18 @@ struct rtc_ops {
         */
        int (*reset)(struct udevice *dev);
 
+       /**
+        * read() - Read multiple 8-bit registers
+        *
+        * @dev:        Device to read from
+        * @reg:        First register to read
+        * @buf:        Output buffer
+        * @len:        Number of registers to read
+        * @return 0 if OK, -ve on error
+        */
+       int (*read)(struct udevice *dev, unsigned int reg,
+                          u8 *buf, unsigned int len);
+
        /**
         * read8() - Read an 8-bit register
         *
@@ -109,6 +121,17 @@ int dm_rtc_set(struct udevice *dev, struct rtc_time *time);
  */
 int dm_rtc_reset(struct udevice *dev);
 
+/**
+ * rtc_read() - Read multiple 8-bit registers
+ *
+ * @dev:       Device to read from
+ * @reg:       First register to read
+ * @buf:       Output buffer
+ * @len:       Number of registers to read
+ * @return 0 if OK, -ve on error
+ */
+int rtc_read(struct udevice *dev, unsigned int reg, u8 *buf, unsigned int len);
+
 /**
  * rtc_read8() - Read an 8-bit register
  *
-- 
2.23.0