From b4c7698dd95f253c6958d8c6ac219098009bf28a Mon Sep 17 00:00:00 2001
From: "Russell King (Oracle)" <rmk+kernel@armlinux.org.uk>
Date: Tue, 3 Dec 2024 15:31:02 +0000
Subject: [PATCH 04/13] net: phy: add phy_inband_caps()

Add a method to query the PHY's in-band capabilities for a PHY
interface mode.

Where the interface mode does not have in-band capability, or the PHY
driver has not been updated to return this information, then
phy_inband_caps() should return zero. Otherwise, PHY drivers will
return a value consisting of the following flags:

LINK_INBAND_DISABLE indicates that the hardware does not support
in-band signalling, or can have in-band signalling configured via
software to be disabled.

LINK_INBAND_ENABLE indicates that the hardware will use in-band
signalling, or can have in-band signalling configured via software
to be enabled.

LINK_INBAND_BYPASS indicates that the hardware has the ability to
bypass in-band signalling when enabled after a timeout if the link
partner does not respond to its in-band signalling.

This reports the PHY capabilities for the particular interface mode,
not the current configuration.

Reviewed-by: Andrew Lunn <andrew@lunn.ch>
Signed-off-by: Russell King (Oracle) <rmk+kernel@armlinux.org.uk>
Link: https://patch.msgid.link/E1tIUre-006ITz-KF@rmk-PC.armlinux.org.uk
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
---
 drivers/net/phy/phy.c | 21 +++++++++++++++++++++
 include/linux/phy.h   | 28 ++++++++++++++++++++++++++++
 2 files changed, 49 insertions(+)

--- a/drivers/net/phy/phy.c
+++ b/drivers/net/phy/phy.c
@@ -1049,6 +1049,27 @@ static int phy_check_link_status(struct
 }
 
 /**
+ * phy_inband_caps - query which in-band signalling modes are supported
+ * @phydev: a pointer to a &struct phy_device
+ * @interface: the interface mode for the PHY
+ *
+ * Returns zero if it is unknown what in-band signalling is supported by the
+ * PHY (e.g. because the PHY driver doesn't implement the method.) Otherwise,
+ * returns a bit mask of the LINK_INBAND_* values from
+ * &enum link_inband_signalling to describe which inband modes are supported
+ * by the PHY for this interface mode.
+ */
+unsigned int phy_inband_caps(struct phy_device *phydev,
+			     phy_interface_t interface)
+{
+	if (phydev->drv && phydev->drv->inband_caps)
+		return phydev->drv->inband_caps(phydev, interface);
+
+	return 0;
+}
+EXPORT_SYMBOL_GPL(phy_inband_caps);
+
+/**
  * _phy_start_aneg - start auto-negotiation for this PHY device
  * @phydev: the phy_device struct
  *
--- a/include/linux/phy.h
+++ b/include/linux/phy.h
@@ -826,6 +826,24 @@ struct phy_tdr_config {
 #define PHY_PAIR_ALL -1
 
 /**
+ * enum link_inband_signalling - in-band signalling modes that are supported
+ *
+ * @LINK_INBAND_DISABLE: in-band signalling can be disabled
+ * @LINK_INBAND_ENABLE: in-band signalling can be enabled without bypass
+ * @LINK_INBAND_BYPASS: in-band signalling can be enabled with bypass
+ *
+ * The possible and required bits can only be used if the valid bit is set.
+ * If possible is clear, that means inband signalling can not be used.
+ * Required is only valid when possible is set, and means that inband
+ * signalling must be used.
+ */
+enum link_inband_signalling {
+	LINK_INBAND_DISABLE		= BIT(0),
+	LINK_INBAND_ENABLE		= BIT(1),
+	LINK_INBAND_BYPASS		= BIT(2),
+};
+
+/**
  * struct phy_plca_cfg - Configuration of the PLCA (Physical Layer Collision
  * Avoidance) Reconciliation Sublayer.
  *
@@ -964,6 +982,14 @@ struct phy_driver {
 	int (*get_features)(struct phy_device *phydev);
 
 	/**
+	 * @inband_caps: query whether in-band is supported for the given PHY
+	 * interface mode. Returns a bitmask of bits defined by enum
+	 * link_inband_signalling.
+	 */
+	unsigned int (*inband_caps)(struct phy_device *phydev,
+				    phy_interface_t interface);
+
+	/**
 	 * @get_rate_matching: Get the supported type of rate matching for a
 	 * particular phy interface. This is used by phy consumers to determine
 	 * whether to advertise lower-speed modes for that interface. It is
@@ -1842,6 +1868,8 @@ int phy_config_aneg(struct phy_device *p
 int _phy_start_aneg(struct phy_device *phydev);
 int phy_start_aneg(struct phy_device *phydev);
 int phy_aneg_done(struct phy_device *phydev);
+unsigned int phy_inband_caps(struct phy_device *phydev,
+			     phy_interface_t interface);
 int phy_speed_down(struct phy_device *phydev, bool sync);
 int phy_speed_up(struct phy_device *phydev);
 bool phy_check_valid(int speed, int duplex, unsigned long *features);
