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/*
 *  include/asm/cnt32_to_63.h -- extend a 32-bit counter to 63 bits
 *
 *  Author:	Nicolas Pitre
 *  Created:	December 3, 2006
 *  Copyright:	MontaVista Software, Inc.
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License version 2
 * as published by the Free Software Foundation.
 */

#ifndef __INCLUDE_CNT32_TO_63_H__
#define __INCLUDE_CNT32_TO_63_H__

#include <linux/compiler.h>
#include <asm/types.h>
#include <asm/byteorder.h>

/*
 * Prototype: u64 cnt32_to_63(u32 cnt)
 * Many hardware clock counters are only 32 bits wide and therefore have
 * a relatively short period making wrap-arounds rather frequent.  This
 * is a problem when implementing sched_clock() for example, where a 64-bit
 * non-wrapping monotonic value is expected to be returned.
 *
 * To overcome that limitation, let's extend a 32-bit counter to 63 bits
 * in a completely lock free fashion. Bits 0 to 31 of the clock are provided
 * by the hardware while bits 32 to 62 are stored in memory.  The top bit in
 * memory is used to synchronize with the hardware clock half-period.  When
 * the top bit of both counters (hardware and in memory) differ then the
 * memory is updated with a new value, incrementing it when the hardware
 * counter wraps around.
 *
 * Because a word store in memory is atomic then the incremented value will
 * always be in synch with the top bit indicating to any potential concurrent
 * reader if the value in memory is up to date or not with regards to the
 * needed increment.  And any race in updating the value in memory is harmless
 * as the same value would simply be stored more than once.
 *
 * The only restriction for the algorithm to work properly is that this
 * code must be executed at least once per each half period of the 32-bit
 * counter to properly update the state bit in memory. This is usually not a
 * problem in practice, but if it is then a kernel timer could be scheduled
 * to manage for this code to be executed often enough.
 *
 * Note that the top bit (bit 63) in the returned value should be considered
 * as garbage.  It is not cleared here because callers are likely to use a
 * multiplier on the returned value which can get rid of the top bit
 * implicitly by making the multiplier even, therefore saving on a runtime
 * clear-bit instruction. Otherwise caller must remember to clear the top
 * bit explicitly.
 */

/* this is used only to give gcc a clue about good code generation */
typedef union {
	struct {
#if defined(__LITTLE_ENDIAN)
		u32 lo, hi;
#elif defined(__BIG_ENDIAN)
		u32 hi, lo;
#endif
	};
	u64 val;
} cnt32_to_63_t;

#define cnt32_to_63(cnt_lo) \
({ \
	static volatile u32 __m_cnt_hi = 0; \
	cnt32_to_63_t __x; \
	__x.hi = __m_cnt_hi; \
	__x.lo = (cnt_lo); \
 	if (unlikely((s32)(__x.hi ^ __x.lo) < 0)) \
		__m_cnt_hi = __x.hi = (__x.hi ^ 0x80000000) + (__x.hi >> 31); \
	__x.val; \
})

#endif
t">; extern rwlock_t llc_sap_list_lock; extern unsigned char llc_station_mac_sa[ETH_ALEN]; extern int llc_rcv(struct sk_buff *skb, struct net_device *dev, struct packet_type *pt, struct net_device *orig_dev); extern int llc_mac_hdr_init(struct sk_buff *skb, const unsigned char *sa, const unsigned char *da); extern void llc_add_pack(int type, void (*handler)(struct llc_sap *sap, struct sk_buff *skb)); extern void llc_remove_pack(int type); extern void llc_set_station_handler(void (*handler)(struct sk_buff *skb)); extern struct llc_sap *llc_sap_open(unsigned char lsap, int (*rcv)(struct sk_buff *skb, struct net_device *dev, struct packet_type *pt, struct net_device *orig_dev)); static inline void llc_sap_hold(struct llc_sap *sap) { atomic_inc(&sap->refcnt); } extern void llc_sap_close(struct llc_sap *sap); static inline void llc_sap_put(struct llc_sap *sap) { if (atomic_dec_and_test(&sap->refcnt)) llc_sap_close(sap); } extern struct llc_sap *llc_sap_find(unsigned char sap_value); extern int llc_build_and_send_ui_pkt(struct llc_sap *sap, struct sk_buff *skb, unsigned char *dmac, unsigned char dsap); extern void llc_sap_handler(struct llc_sap *sap, struct sk_buff *skb); extern void llc_conn_handler(struct llc_sap *sap, struct sk_buff *skb); extern int llc_station_init(void); extern void llc_station_exit(void); #ifdef CONFIG_PROC_FS extern int llc_proc_init(void); extern void llc_proc_exit(void); #else #define llc_proc_init() (0) #define llc_proc_exit() do { } while(0) #endif /* CONFIG_PROC_FS */ #ifdef CONFIG_SYSCTL extern int llc_sysctl_init(void); extern void llc_sysctl_exit(void); extern int sysctl_llc2_ack_timeout; extern int sysctl_llc2_busy_timeout; extern int sysctl_llc2_p_timeout; extern int sysctl_llc2_rej_timeout; extern int sysctl_llc_station_ack_timeout; #else #define llc_sysctl_init() (0) #define llc_sysctl_exit() do { } while(0) #endif /* CONFIG_SYSCTL */ #endif /* LLC_H */