Device Polling code for -current.

Non-SMP, i386-only, no polling in the idle loop at the moment.

To use this code you must compile a kernel with

        options DEVICE_POLLING

and at runtime enable polling with

        sysctl kern.polling.enable=1

The percentage of CPU reserved to userland can be set with

        sysctl kern.polling.user_frac=NN (default is 50)

while the remainder is used by polling device drivers and netisr's.
These are the only two variables that you should need to touch. There
are a few more parameters in kern.polling but the default values
are adequate for all purposes. See the code in kern_poll.c for
more details on them.

Polling in the idle loop will be implemented shortly by introducing
a kernel thread which does the job. Until then, the amount of CPU
dedicated to polling will never exceed (100-user_frac).
The equivalent (actually, better) code for -stable is at

	http://info.iet.unipi.it/~luigi/polling/

and also supports polling in the idle loop.

NOTE to Alpha developers:
There is really nothing in this code that is i386-specific.
If you move the 2 lines supporting the new option from
sys/conf/{files,options}.i386 to sys/conf/{files,options} I am
pretty sure that this should work on the Alpha as well, just that
I do not have a suitable test box to try it. If someone feels like
trying it, I would appreciate it.

NOTE to other developers:
sure some things could be done better, and as always I am open to
constructive criticism, which a few of you have already given and
I greatly appreciated.
However, before proposing radical architectural changes, please
take some time to possibly try out this code, or at the very least
read the comments in kern_poll.c, especially re. the reason why I
am using a soft netisr and cannot (I believe) replace it with a
simple timeout.

Quick description of files touched by this commit:

sys/conf/files.i386
        new file kern/kern_poll.c
sys/conf/options.i386
        new option
sys/i386/i386/trap.c
        poll in trap (disabled by default)
sys/kern/kern_clock.c
        initialization and hardclock hooks.
sys/kern/kern_intr.c
        minor swi_net changes
sys/kern/kern_poll.c
        the bulk of the code.
sys/net/if.h
        new flag
sys/net/if_var.h
        declaration for functions used in device drivers.
sys/net/netisr.h
        NETISR_POLL
sys/dev/fxp/if_fxp.c
sys/dev/fxp/if_fxpvar.h
sys/pci/if_dc.c
sys/pci/if_dcreg.h
sys/pci/if_sis.c
sys/pci/if_sisreg.h
        device driver modifications

3 files changed, 19 insertions, 0 deletions

diff --git a/sys/net/if.h b/sys/net/if.h
index 83116b9..6cc5522 100644
--- a/sys/net/if.h
+++ b/sys/net/if.h
@@ -131,6 +131,15 @@ struct if_data {
 #define	IFF_ALTPHYS	IFF_LINK2	/* use alternate physical connection */
 #define	IFF_MULTICAST	0x8000		/* supports multicast */
 
+/*
+ * The following flag(s) ought to go in if_flags, but we cannot change
+ * struct ifnet because of binary compatibility, so we store them in
+ * if_ipending, which is not used so far.
+ * If possible, make sure the value is not conflicting with other
+ * IFF flags, so we have an easier time when we want to merge them.
+ */
+#define	IFF_POLLING	0x10000		/* Interface is in polling mode. */
+
 /* flags set internally only: */
 #define	IFF_CANTCHANGE \
 	(IFF_BROADCAST|IFF_POINTOPOINT|IFF_RUNNING|IFF_OACTIVE|\
diff --git a/sys/net/if_var.h b/sys/net/if_var.h
index 58d3780..dacea63 100644
--- a/sys/net/if_var.h
+++ b/sys/net/if_var.h
@@ -459,6 +459,15 @@ int	if_clone_destroy __P((const char *));
 #define IF_LLADDR(ifp)							\
     LLADDR((struct sockaddr_dl *) ifaddr_byindex((ifp)->if_index)->ifa_addr)
 
+#ifdef DEVICE_POLLING
+enum poll_cmd {	POLL_ONLY, POLL_AND_CHECK_STATUS, POLL_DEREGISTER };
+
+typedef	void poll_handler_t __P((struct ifnet *ifp,
+		enum poll_cmd cmd, int count));
+int    ether_poll_register __P((poll_handler_t *h, struct ifnet *ifp));
+int    ether_poll_deregister __P((struct ifnet *ifp));
+#endif /* DEVICE_POLLING */
+
 #endif /* _KERNEL */
 
 #endif /* !_NET_IF_VAR_H_ */
diff --git a/sys/net/netisr.h b/sys/net/netisr.h
index 621cf22..35e8cc1 100644
--- a/sys/net/netisr.h
+++ b/sys/net/netisr.h
@@ -52,6 +52,7 @@
  * interrupt used for scheduling the network code to calls
  * on the lowest level routine of each protocol.
  */
+#define	NETISR_POLL	0		/* polling callback, must be first */
 #define	NETISR_IP	2		/* same as AF_INET */
 #define	NETISR_NS	6		/* same as AF_NS */
 #define	NETISR_ATALK    16              /* same as AF_APPLETALK */