sfp: add documentation for kernel APIs

Add kernel-doc documentation for sfp kernel APIs, and link it into the
networking kapi documentation under "Network device support".

Signed-off-by: Russell King <rmk+kernel@armlinux.org.uk>
Reviewed-by: Florian Fainelli <f.fainelli@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

3 files changed, 152 insertions, 14 deletions

diff --git a/Documentation/networking/kapi.rst b/Documentation/networking/kapi.rst
index df4141b72f24..f03ae64be8bc 100644
--- a/Documentation/networking/kapi.rst
+++ b/Documentation/networking/kapi.rst
@@ -157,3 +157,15 @@ PHYLINK
    :internal:
 
 .. kernel-doc:: drivers/net/phy/phylink.c
+
+SFP support
+-----------
+
+.. kernel-doc:: drivers/net/phy/sfp-bus.c
+   :internal:
+
+.. kernel-doc:: include/linux/sfp.h
+   :internal:
+
+.. kernel-doc:: drivers/net/phy/sfp-bus.c
+   :export:
diff --git a/drivers/net/phy/sfp-bus.c b/drivers/net/phy/sfp-bus.c
index 8a1b1f4c1b7c..2b8c256156a2 100644
--- a/drivers/net/phy/sfp-bus.c
+++ b/drivers/net/phy/sfp-bus.c
@@ -8,7 +8,11 @@
 
 #include "sfp.h"
 
+/**
+ * struct sfp_bus - internal representation of a sfp bus
+ */
 struct sfp_bus {
+	/* private: */
 	struct kref kref;
 	struct list_head node;
 	struct device_node *device_node;
@@ -26,6 +30,20 @@ struct sfp_bus {
 	bool started;
 };
 
+/**
+ * sfp_parse_port() - Parse the EEPROM base ID, setting the port type
+ * @bus: a pointer to the &struct sfp_bus structure for the sfp module
+ * @id: a pointer to the module's &struct sfp_eeprom_id
+ * @support: optional pointer to an array of unsigned long for the
+ *   ethtool support mask
+ *
+ * Parse the EEPROM identification given in @id, and return one of
+ * %PORT_TP, %PORT_FIBRE or %PORT_OTHER. If @support is non-%NULL,
+ * also set the ethtool %ETHTOOL_LINK_MODE_xxx_BIT corresponding with
+ * the connector type.
+ *
+ * If the port type is not known, returns %PORT_OTHER.
+ */
 int sfp_parse_port(struct sfp_bus *bus, const struct sfp_eeprom_id *id,
 		   unsigned long *support)
 {
@@ -78,6 +96,24 @@ int sfp_parse_port(struct sfp_bus *bus, const struct sfp_eeprom_id *id,
 }
 EXPORT_SYMBOL_GPL(sfp_parse_port);
 
+/**
+ * sfp_parse_interface() - Parse the phy_interface_t
+ * @bus: a pointer to the &struct sfp_bus structure for the sfp module
+ * @id: a pointer to the module's &struct sfp_eeprom_id
+ *
+ * Derive the phy_interface_t mode for the information found in the
+ * module's identifying EEPROM. There is no standard or defined way
+ * to derive this information, so we use some heuristics.
+ *
+ * If the encoding is 64b66b, then the module must be >= 10G, so
+ * return %PHY_INTERFACE_MODE_10GKR.
+ *
+ * If it's 8b10b, then it's 1G or slower. If it's definitely a fibre
+ * module, return %PHY_INTERFACE_MODE_1000BASEX mode, otherwise return
+ * %PHY_INTERFACE_MODE_SGMII mode.
+ *
+ * If the encoding is not known, return %PHY_INTERFACE_MODE_NA.
+ */
 phy_interface_t sfp_parse_interface(struct sfp_bus *bus,
 				    const struct sfp_eeprom_id *id)
 {
@@ -117,6 +153,15 @@ phy_interface_t sfp_parse_interface(struct sfp_bus *bus,
 }
 EXPORT_SYMBOL_GPL(sfp_parse_interface);
 
+/**
+ * sfp_parse_support() - Parse the eeprom id for supported link modes
+ * @bus: a pointer to the &struct sfp_bus structure for the sfp module
+ * @id: a pointer to the module's &struct sfp_eeprom_id
+ * @support: pointer to an array of unsigned long for the ethtool support mask
+ *
+ * Parse the EEPROM identification information and derive the supported
+ * ethtool link modes for the module.
+ */
 void sfp_parse_support(struct sfp_bus *bus, const struct sfp_eeprom_id *id,
 		       unsigned long *support)
 {
@@ -293,6 +338,16 @@ static void sfp_unregister_bus(struct sfp_bus *bus)
 	bus->registered = false;
 }
 
+/**
+ * sfp_get_module_info() - Get the ethtool_modinfo for a SFP module
+ * @bus: a pointer to the &struct sfp_bus structure for the sfp module
+ * @modinfo: a &struct ethtool_modinfo
+ *
+ * Fill in the type and eeprom_len parameters in @modinfo for a module on
+ * the sfp bus specified by @bus.
+ *
+ * Returns 0 on success or a negative errno number.
+ */
 int sfp_get_module_info(struct sfp_bus *bus, struct ethtool_modinfo *modinfo)
 {
 	if (!bus->registered)
@@ -301,6 +356,17 @@ int sfp_get_module_info(struct sfp_bus *bus, struct ethtool_modinfo *modinfo)
 }
 EXPORT_SYMBOL_GPL(sfp_get_module_info);
 
+/**
+ * sfp_get_module_eeprom() - Read the SFP module EEPROM
+ * @bus: a pointer to the &struct sfp_bus structure for the sfp module
+ * @ee: a &struct ethtool_eeprom
+ * @data: buffer to contain the EEPROM data (must be at least @ee->len bytes)
+ *
+ * Read the EEPROM as specified by the supplied @ee. See the documentation
+ * for &struct ethtool_eeprom for the region to be read.
+ *
+ * Returns 0 on success or a negative errno number.
+ */
 int sfp_get_module_eeprom(struct sfp_bus *bus, struct ethtool_eeprom *ee,
 			  u8 *data)
 {
@@ -310,6 +376,15 @@ int sfp_get_module_eeprom(struct sfp_bus *bus, struct ethtool_eeprom *ee,
 }
 EXPORT_SYMBOL_GPL(sfp_get_module_eeprom);
 
+/**
+ * sfp_upstream_start() - Inform the SFP that the network device is up
+ * @bus: a pointer to the &struct sfp_bus structure for the sfp module
+ *
+ * Inform the SFP socket that the network device is now up, so that the
+ * module can be enabled by allowing TX_DISABLE to be deasserted. This
+ * should be called from the network device driver's &struct net_device_ops
+ * ndo_open() method.
+ */
 void sfp_upstream_start(struct sfp_bus *bus)
 {
 	if (bus->registered)
@@ -318,6 +393,15 @@ void sfp_upstream_start(struct sfp_bus *bus)
 }
 EXPORT_SYMBOL_GPL(sfp_upstream_start);
 
+/**
+ * sfp_upstream_stop() - Inform the SFP that the network device is down
+ * @bus: a pointer to the &struct sfp_bus structure for the sfp module
+ *
+ * Inform the SFP socket that the network device is now up, so that the
+ * module can be disabled by asserting TX_DISABLE, disabling the laser
+ * in optical modules. This should be called from the network device
+ * driver's &struct net_device_ops ndo_stop() method.
+ */
 void sfp_upstream_stop(struct sfp_bus *bus)
 {
 	if (bus->registered)
@@ -326,6 +410,19 @@ void sfp_upstream_stop(struct sfp_bus *bus)
 }
 EXPORT_SYMBOL_GPL(sfp_upstream_stop);
 
+/**
+ * sfp_register_upstream() - Register the neighbouring device
+ * @np: device node for the SFP bus
+ * @ndev: network device associated with the interface
+ * @upstream: the upstream private data
+ * @ops: the upstream's &struct sfp_upstream_ops
+ *
+ * Register the upstream device (eg, PHY) with the SFP bus. MAC drivers
+ * should use phylink, which will call this function for them. Returns
+ * a pointer to the allocated &struct sfp_bus.
+ *
+ * On error, returns %NULL.
+ */
 struct sfp_bus *sfp_register_upstream(struct device_node *np,
 				      struct net_device *ndev, void *upstream,
 				      const struct sfp_upstream_ops *ops)
@@ -353,6 +450,13 @@ struct sfp_bus *sfp_register_upstream(struct device_node *np,
 }
 EXPORT_SYMBOL_GPL(sfp_register_upstream);
 
+/**
+ * sfp_unregister_upstream() - Unregister sfp bus
+ * @bus: a pointer to the &struct sfp_bus structure for the sfp module
+ *
+ * Unregister a previously registered upstream connection for the SFP
+ * module. @bus is returned from sfp_register_upstream().
+ */
 void sfp_unregister_upstream(struct sfp_bus *bus)
 {
 	rtnl_lock();
diff --git a/include/linux/sfp.h b/include/linux/sfp.h
index 4a906f560817..b6089fe72378 100644
--- a/include/linux/sfp.h
+++ b/include/linux/sfp.h
@@ -3,7 +3,7 @@
 
 #include <linux/phy.h>
 
-struct __packed sfp_eeprom_base {
+struct sfp_eeprom_base {
 	u8 phys_id;
 	u8 phys_ext_id;
 	u8 connector;
@@ -166,12 +166,12 @@ struct __packed sfp_eeprom_base {
 	union {
 		__be16 optical_wavelength;
 		u8 cable_spec;
-	};
+	} __packed;
 	u8 reserved62;
 	u8 cc_base;
-};
+} __packed;
 
-struct __packed sfp_eeprom_ext {
+struct sfp_eeprom_ext {
 	__be16 options;
 	u8 br_max;
 	u8 br_min;
@@ -181,12 +181,21 @@ struct __packed sfp_eeprom_ext {
 	u8 enhopts;
 	u8 sff8472_compliance;
 	u8 cc_ext;
-};
-
-struct __packed sfp_eeprom_id {
+} __packed;
+
+/**
+ * struct sfp_eeprom_id - raw SFP module identification information
+ * @base: base SFP module identification structure
+ * @ext: extended SFP module identification structure
+ *
+ * See the SFF-8472 specification and related documents for the definition
+ * of these structure members. This can be obtained from
+ * ftp://ftp.seagate.com/sff
+ */
+struct sfp_eeprom_id {
 	struct sfp_eeprom_base base;
 	struct sfp_eeprom_ext ext;
-};
+} __packed;
 
 /* SFP EEPROM registers */
 enum {
@@ -353,13 +362,26 @@ struct ethtool_modinfo;
 struct net_device;
 struct sfp_bus;
 
+/**
+ * struct sfp_upstream_ops - upstream operations structure
+ * @module_insert: called after a module has been detected to determine
+ *   whether the module is supported for the upstream device.
+ * @module_remove: called after the module has been removed.
+ * @link_down: called when the link is non-operational for whatever
+ *   reason.
+ * @link_up: called when the link is operational.
+ * @connect_phy: called when an I2C accessible PHY has been detected
+ *   on the module.
+ * @disconnect_phy: called when a module with an I2C accessible PHY has
+ *   been removed.
+ */
 struct sfp_upstream_ops {
-	int (*module_insert)(void *, const struct sfp_eeprom_id *id);
-	void (*module_remove)(void *);
-	void (*link_down)(void *);
-	void (*link_up)(void *);
-	int (*connect_phy)(void *, struct phy_device *);
-	void (*disconnect_phy)(void *);
+	int (*module_insert)(void *priv, const struct sfp_eeprom_id *id);
+	void (*module_remove)(void *priv);
+	void (*link_down)(void *priv);
+	void (*link_up)(void *priv);
+	int (*connect_phy)(void *priv, struct phy_device *);
+	void (*disconnect_phy)(void *priv);
 };
 
 #if IS_ENABLED(CONFIG_SFP)