Index: stand/libsa/libsa.3
===================================================================
--- stand/libsa/libsa.3
+++ stand/libsa/libsa.3
@@ -24,7 +24,7 @@
 .\"
 .\" $FreeBSD$
 .\"
-.Dd February 22, 2018
+.Dd August 1, 2022
 .Dt LIBSA 3
 .Os
 .Sh NAME
@@ -687,6 +687,56 @@
 Devices are exported by the supporting code via the array
 .Vt struct devsw *devsw[]
 which is a NULL terminated array of pointers to device switch structures.
+.Sh DRIVER INTERFACE
+The driver needs to provide a common set of entry points that are
+used by
+.Nm libsa
+to interface with the device.
+.Bd -literal
+struct devsw {
+    const char	dv_name[DEV_NAMLEN];
+    int		dv_type;
+    int		(*dv_init)(void);
+    int		(*dv_strategy)(void *devdata, int rw, daddr_t blk,
+			size_t size, char *buf, size_t *rsize);
+    int		(*dv_open)(struct open_file *f, ...);
+    int		(*dv_close)(struct open_file *f);
+    int		(*dv_ioctl)(struct open_file *f, u_long cmd, void *data);
+    int		(*dv_print)(int verbose);
+    void	(*dv_cleanup)(void);
+    void	(*dv_fmtdev)(struct devdesc *);
+};
+.Ed
+.Bl -tag -width ".Fn dv_strategy"
+.It Fn dv_name
+The device's name.
+.It Fn dv_type
+Class of device.
+Each class will potentially have a different subclass of
+.Dv struct devdesc.
+.It Fn dv_init
+Driver initialization routine.
+This routine should probe for available units.
+Drivers are responsible for maintaining lists of units for later enumeration.
+No other driver routines may be called before
+.Fn dv_init
+returns.
+.It Fn dv_open
+The driver open routine.
+.It Fn dv_close
+The driver close routine.
+.It Fn dv_ioctl
+The driver ioctl routine.
+.It Fn dv_print
+Prints information about the available devices.
+Information should be presented with
+.Fn pager_output .
+.It Fn dv_cleanup
+Cleans up any memory used by the device before the next stage is run.
+.It Fn dv_fmtdev
+Converts the passed in devdesc to the canonical string representation
+for that device.
+.El
 .Sh HISTORY
 The
 .Nm