net: ethtool: add new ETHTOOL_xLINKSETTINGS API

This patch defines a new ETHTOOL_GLINKSETTINGS/SLINKSETTINGS API,
handled by the new get_link_ksettings/set_link_ksettings callbacks.
This API provides support for most legacy ethtool_cmd fields, adds
support for larger link mode masks (up to 4064 bits, variable length),
and removes ethtool_cmd deprecated
fields (transceiver/maxrxpkt/maxtxpkt).

This API is deprecating the legacy ETHTOOL_GSET/SSET API and provides
the following backward compatibility properties:
 - legacy ethtool with legacy drivers: no change, still using the
   get_settings/set_settings callbacks.
 - legacy ethtool with new get/set_link_ksettings drivers: the new
   driver callbacks are used, data internally converted to legacy
   ethtool_cmd. ETHTOOL_GSET will return only the 1st 32b of each link
   mode mask. ETHTOOL_SSET will fail if user tries to set the
   ethtool_cmd deprecated fields to
   non-0 (transceiver/maxrxpkt/maxtxpkt). A kernel warning is logged if
   driver sets higher bits.
 - future ethtool with legacy drivers: no change, still using the
   get_settings/set_settings callbacks, internally converted to new data
   structure. Deprecated fields (transceiver/maxrxpkt/maxtxpkt) will be
   ignored and seen as 0 from user space. Note that that "future"
   ethtool tool will not allow changes to these deprecated fields.
 - future ethtool with new drivers: direct call to the new callbacks.

By "future" ethtool, what is meant is:
 - query: first try ETHTOOL_GLINKSETTINGS, and revert to ETHTOOL_GSET if
   fails
 - set: query first and remember which of ETHTOOL_GLINKSETTINGS or
   ETHTOOL_GSET was successful
   + if ETHTOOL_GLINKSETTINGS was successful, then change config with
     ETHTOOL_SLINKSETTINGS. A failure there is final (do not try
     ETHTOOL_SSET).
   + otherwise ETHTOOL_GSET was successful, change config with
     ETHTOOL_SSET. A failure there is final (do not try
     ETHTOOL_SLINKSETTINGS).

The interaction user/kernel via the new API requires a small
ETHTOOL_GLINKSETTINGS handshake first to agree on the length of the link
mode bitmaps. If kernel doesn't agree with user, it returns the bitmap
length it is expecting from user as a negative length (and cmd field is
0). When kernel and user agree, kernel returns valid info in all
fields (ie. link mode length > 0 and cmd is ETHTOOL_GLINKSETTINGS).

Data structure crossing user/kernel boundary is 32/64-bit
agnostic. Converted internally to a legal kernel bitmap.

The internal __ethtool_get_settings kernel helper will gradually be
replaced by __ethtool_get_link_ksettings by the time the first
"link_settings" drivers start to appear. So this patch doesn't change
it, it will be removed before it needs to be changed.

Signed-off-by: David Decotigny <decot@googlers.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

Author: David Decotigny

include/linux/ethtool.h

@@ -12,6 +12,7 @@
 #ifndef _LINUX_ETHTOOL_H
 #define _LINUX_ETHTOOL_H
 
+#include <linux/bitmap.h>
 #include <linux/compat.h>
 #include <uapi/linux/ethtool.h>
 
@@ -40,9 +41,6 @@ struct compat_ethtool_rxnfc {
 
 #include <linux/rculist.h>
 
-extern int __ethtool_get_settings(struct net_device *dev,
-				  struct ethtool_cmd *cmd);
-
 /**
  * enum ethtool_phys_id_state - indicator state for physical identification
  * @ETHTOOL_ID_INACTIVE: Physical ID indicator should be deactivated
@@ -97,13 +95,74 @@ static inline u32 ethtool_rxfh_indir_default(u32 index, u32 n_rx_rings)
 	return index % n_rx_rings;
 }
 
+/* number of link mode bits/ulongs handled internally by kernel */
+#define __ETHTOOL_LINK_MODE_MASK_NBITS			\
+	(__ETHTOOL_LINK_MODE_LAST + 1)
+
+/* declare a link mode bitmap */
+#define __ETHTOOL_DECLARE_LINK_MODE_MASK(name)		\
+	DECLARE_BITMAP(name, __ETHTOOL_LINK_MODE_MASK_NBITS)
+
+/* drivers must ignore base.cmd and base.link_mode_masks_nwords
+ * fields, but they are allowed to overwrite them (will be ignored).
+ */
+struct ethtool_link_ksettings {
+	struct ethtool_link_settings base;
+	struct {
+		__ETHTOOL_DECLARE_LINK_MODE_MASK(supported);
+		__ETHTOOL_DECLARE_LINK_MODE_MASK(advertising);
+		__ETHTOOL_DECLARE_LINK_MODE_MASK(lp_advertising);
+	} link_modes;
+};
+
+/**
+ * ethtool_link_ksettings_zero_link_mode - clear link_ksettings link mode mask
+ *   @ptr : pointer to struct ethtool_link_ksettings
+ *   @name : one of supported/advertising/lp_advertising
+ */
+#define ethtool_link_ksettings_zero_link_mode(ptr, name)		\
+	bitmap_zero((ptr)->link_modes.name, __ETHTOOL_LINK_MODE_MASK_NBITS)
+
+/**
+ * ethtool_link_ksettings_add_link_mode - set bit in link_ksettings
+ * link mode mask
+ *   @ptr : pointer to struct ethtool_link_ksettings
+ *   @name : one of supported/advertising/lp_advertising
+ *   @mode : one of the ETHTOOL_LINK_MODE_*_BIT
+ * (not atomic, no bound checking)
+ */
+#define ethtool_link_ksettings_add_link_mode(ptr, name, mode)		\
+	__set_bit(ETHTOOL_LINK_MODE_ ## mode ## _BIT, (ptr)->link_modes.name)
+
+/**
+ * ethtool_link_ksettings_test_link_mode - test bit in ksettings link mode mask
+ *   @ptr : pointer to struct ethtool_link_ksettings
+ *   @name : one of supported/advertising/lp_advertising
+ *   @mode : one of the ETHTOOL_LINK_MODE_*_BIT
+ * (not atomic, no bound checking)
+ *
+ * Returns true/false.
+ */
+#define ethtool_link_ksettings_test_link_mode(ptr, name, mode)		\
+	test_bit(ETHTOOL_LINK_MODE_ ## mode ## _BIT, (ptr)->link_modes.name)
+
+extern int
+__ethtool_get_link_ksettings(struct net_device *dev,
+			     struct ethtool_link_ksettings *link_ksettings);
+
+/* DEPRECATED, use __ethtool_get_link_ksettings */
+extern int __ethtool_get_settings(struct net_device *dev,
+				  struct ethtool_cmd *cmd);
+
 /**
  * struct ethtool_ops - optional netdev operations
- * @get_settings: Get various device settings including Ethernet link
+ * @get_settings: DEPRECATED, use %get_link_ksettings/%set_link_ksettings
+ *	API. Get various device settings including Ethernet link
  *	settings. The @cmd parameter is expected to have been cleared
- *	before get_settings is called. Returns a negative error code or
- *	zero.
- * @set_settings: Set various device settings including Ethernet link
+ *	before get_settings is called. Returns a negative error code
+ *	or zero.
+ * @set_settings: DEPRECATED, use %get_link_ksettings/%set_link_ksettings
+ *	API. Set various device settings including Ethernet link
  *	settings.  Returns a negative error code or zero.
  * @get_drvinfo: Report driver/device information.  Should only set the
  *	@driver, @version, @fw_version and @bus_info fields.  If not
@@ -211,6 +270,19 @@ static inline u32 ethtool_rxfh_indir_default(u32 index, u32 n_rx_rings)
  *	a TX queue has this number, return -EINVAL. If only a RX queue or a TX
  *	queue has this number, ignore the inapplicable fields.
  *	Returns a negative error code or zero.
+ * @get_link_ksettings: When defined, takes precedence over the
+ *	%get_settings method. Get various device settings
+ *	including Ethernet link settings. The %cmd and
+ *	%link_mode_masks_nwords fields should be ignored (use
+ *	%__ETHTOOL_LINK_MODE_MASK_NBITS instead of the latter), any
+ *	change to them will be overwritten by kernel. Returns a
+ *	negative error code or zero.
+ * @set_link_ksettings: When defined, takes precedence over the
+ *	%set_settings method. Set various device settings including
+ *	Ethernet link settings. The %cmd and %link_mode_masks_nwords
+ *	fields should be ignored (use %__ETHTOOL_LINK_MODE_MASK_NBITS
+ *	instead of the latter), any change to them will be overwritten
+ *	by kernel. Returns a negative error code or zero.
  *
  * All operations are optional (i.e. the function pointer may be set
  * to %NULL) and callers must take this into account.  Callers must
@@ -293,6 +365,9 @@ struct ethtool_ops {
 					  struct ethtool_coalesce *);
 	int	(*set_per_queue_coalesce)(struct net_device *, u32,
 					  struct ethtool_coalesce *);
-
+	int	(*get_link_ksettings)(struct net_device *,
+				      struct ethtool_link_ksettings *);
+	int	(*set_link_ksettings)(struct net_device *,
+				      const struct ethtool_link_ksettings *);
 };
 #endif /* _LINUX_ETHTOOL_H */