[PATCH net-next v4 2/4] net: phy: Add a helper to return the index for of the internal delay

[Dan Murphy <dmurphy@xxxxxx>]

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 | 51 ++++++++++++++++++++++++++++++++++++
 include/linux/phy.h          |  2 ++
 2 files changed, 53 insertions(+)

diff --git a/drivers/net/phy/phy_device.c b/drivers/net/phy/phy_device.c
index 6b30d205642f..3f3bd0fea53c 100644
--- a/drivers/net/phy/phy_device.c
+++ b/drivers/net/phy/phy_device.c
@@ -2661,6 +2661,57 @@ 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
+ * @int_delay: the internal delay to be looked up
+ *
+ * Returns the index within the array of internal delay passed in.
+ * The array must be in ascending order.
+ * Return errno if the delay is invalid or cannot be found.
+ */
+s32 phy_get_delay_index(struct phy_device *phydev, const int *delay_values,
+			int size, int int_delay)
+{
+	int i;
+
+	if (int_delay < 0)
+		return -EINVAL;
+
+	if (size <= 0)
+		return -EINVAL;
+
+	if (int_delay < delay_values[0] || int_delay > delay_values[size - 1]) {
+		phydev_err(phydev, "Delay %d is out of range\n", int_delay);
+		return -EINVAL;
+	}
+
+	if (int_delay == delay_values[0])
+		return 0;
+
+	for (i = 1; i < size; i++) {
+		if (int_delay == delay_values[i])
+			return i;
+
+		/* Find an approximate index by looking up the table */
+		if (int_delay > delay_values[i - 1] &&
+		    int_delay < delay_values[i]) {
+			if (int_delay - delay_values[i - 1] <
+			    delay_values[i] - int_delay)
+				return i - 1;
+			else
+				return i;
+		}
+	}
+
+	phydev_err(phydev, "error finding internal delay index for %d\n",
+		   int_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 2bcdf19ed3b4..2058ed11f7dd 100644
--- a/include/linux/phy.h
+++ b/include/linux/phy.h
@@ -1408,6 +1408,8 @@ 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, const 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