[PATCH net-next v3 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 | 94 ++++++++++++++++++++++++++++++++++++
 include/linux/phy.h          |  2 +
 2 files changed, 96 insertions(+)

diff --git a/drivers/net/phy/phy_device.c b/drivers/net/phy/phy_device.c
index 6b30d205642f..667b510c8810 100644
--- a/drivers/net/phy/phy_device.c
+++ b/drivers/net/phy/phy_device.c
@@ -2661,6 +2661,100 @@ void phy_get_pause(struct phy_device *phydev, bool *tx_pause, bool *rx_pause)
 }
 EXPORT_SYMBOL(phy_get_pause);
 
+static int phy_find_descending_delay(struct phy_device *phydev,
+				     int *delay_values, int size, int int_delay)
+{
+	int i;
+
+	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;
+}
+
+static int phy_find_ascending_delay(struct phy_device *phydev,
+				    int *delay_values, int size, int int_delay)
+{
+	int i;
+
+	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;
+}
+
+/**
+ * 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
+ * @descending: if the delay array is in descending order
+ *
+ * Returns the index within the array of internal delay passed in.
+ * Return errno if the delay is invalid or cannot be found.
+ */
+s32 phy_get_delay_index(struct phy_device *phydev, int *delay_values, int size,
+			int int_delay, bool descending)
+{
+	if (int_delay < 0)
+		return -EINVAL;
+
+	if (size <= 0)
+		return -EINVAL;
+
+	if (descending)
+		return phy_find_descending_delay(phydev, delay_values, size,
+						 int_delay);
+
+	return phy_find_ascending_delay(phydev, delay_values, size, int_delay);
+}
+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..1ba2c132b635 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, int *delay_values,
+			int size, int delay, bool descending);
 void phy_resolve_pause(unsigned long *local_adv, unsigned long *partner_adv,
 		       bool *tx_pause, bool *rx_pause);
 
-- 
2.26.2