[RFC PATCH net-next 2/4] net: phy: Add a helper to return the index for of the internal delay

[Dan Murphy]

Add a helper function that will return the index in the array for the
passed in internal delay value.  The helper requires the array, size and
delay value.

The helper will then return the index for the exact match or return the
index for the index to the closest smaller value.

Signed-off-by: Dan Murphy <dmurphy@xxxxxx>
---
 drivers/net/phy/phy_device.c | 45 ++++++++++++++++++++++++++++++++++++
 include/linux/phy.h          |  2 ++
 2 files changed, 47 insertions(+)

diff --git a/drivers/net/phy/phy_device.c b/drivers/net/phy/phy_device.c
index 7481135d27ab..40f53b379d2b 100644
--- a/drivers/net/phy/phy_device.c
+++ b/drivers/net/phy/phy_device.c
@@ -2661,6 +2661,51 @@ void phy_get_pause(struct phy_device *phydev, bool *tx_pause, bool *rx_pause)
 }
 EXPORT_SYMBOL(phy_get_pause);
 
+/**
+ * phy_get_delay_index - returns the index of the internal delay
+ * @phydev: phy_device struct
+ * @delay_values: array of delays the PHY supports
+ * @size: the size of the delay array
+ * @delay: the delay to be looked up
+ *
+ * Returns the index within the array of internal delay passed in.
+ */
+int phy_get_delay_index(struct phy_device *phydev, int *delay_values, int size,
+			int delay)
+{
+	int i;
+
+	if (size <= 0)
+		return -EINVAL;
+
+	if (delay <= delay_values[0])
+		return 0;
+
+	if (delay > delay_values[size - 1])
+		return size - 1;
+
+	for (i = 0; i < size; i++) {
+		if (delay == delay_values[i])
+			return i;
+
+		/* Find an approximate index by looking up the table */
+		if (delay > delay_values[i - 1] &&
+		    delay < delay_values[i]) {
+			if (delay - delay_values[i - 1] < delay_values[i] - delay)
+				return i - 1;
+			else
+				return i;
+		}
+
+	}
+
+	phydev_err(phydev, "error finding internal delay index for %d\n",
+		   delay);
+
+	return -EINVAL;
+}
+EXPORT_SYMBOL(phy_get_delay_index);
+
 static bool phy_drv_supports_irq(struct phy_driver *phydrv)
 {
 	return phydrv->config_intr && phydrv->ack_interrupt;
diff --git a/include/linux/phy.h b/include/linux/phy.h
index 467aa8bf9f64..78b7b77f9a67 100644
--- a/include/linux/phy.h
+++ b/include/linux/phy.h
@@ -1406,6 +1406,8 @@ void phy_set_asym_pause(struct phy_device *phydev, bool rx, bool tx);
 bool phy_validate_pause(struct phy_device *phydev,
 			struct ethtool_pauseparam *pp);
 void phy_get_pause(struct phy_device *phydev, bool *tx_pause, bool *rx_pause);
+int phy_get_delay_index(struct phy_device *phydev, int *delay_values,
+			int size, int delay);
 void phy_resolve_pause(unsigned long *local_adv, unsigned long *partner_adv,
 		       bool *tx_pause, bool *rx_pause);
 
-- 
2.26.2