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Took out the call to schedule() that we were doing after a write to the
log, since it didn't seem to have any effect on the reliability of
streaming data but still ends up costing the calling process some time.

Banner including version number now emitted to kernel log when module
is inserted.  Added version number constant to header file.

General cleanup: more consistent use of macros, etc.

Now compiles cleanly with -Wall (why didn't I do this before?)

/*
 * EMLOG: the EMbedded-device LOGger
 *
 * Jeremy Elson <jelson@circlemud.org>
 * USC/Information Sciences Institute
 *
 * This code is released under the GPL
 *
 * This is emlog version 0.40, released 13 August 2001
 * For more information see http://www.circlemud.org/~jelson/software/emlog
 *
 * $Id: emlog.h,v 1.5 2001/08/13 21:12:48 jelson Exp $
 */

#define EMLOG_MAJOR_NUMBER   241
#define EMLOG_MAX_SIZE       128 /* max size in kilobytes of a buffer */

#define EMLOG_VERSION        "0.40"

/************************ Private Definitions *****************************/

struct emlog_info {

#if defined(DECLARE_WAIT_QUEUE_HEAD)
  wait_queue_head_t read_q;
#else
  struct wait_queue *read_q;
#endif
  
  unsigned long i_ino;		/* Inode number of this emlog buffer */
  char *data;			/* The circular buffer data */
  int size;			/* Size of the buffer pointed to by 'data' */
  int refcount;			/* Files that have this buffer open */
  int read_point;		/* Offset in circ. buffer of oldest data */
  int write_point;		/* Offset in circ. buffer of newest data */
  int offset;			/* Byte number of read_point in the stream */
  struct emlog_info *next;
};


/* amount of data in the queue */
#define EMLOG_QLEN(einfo) ( (einfo)->write_point >= (einfo)->read_point ? \
         (einfo)->write_point - (einfo)->read_point : \
         (einfo)->size - (einfo)->read_point + (einfo)->write_point)

/* byte number of the last byte in the queue */
#define EMLOG_FIRST_EMPTY_BYTE(einfo) ((einfo)->offset + EMLOG_QLEN(einfo))
			
/* macro to make it more convenient to access the wait q */
#define EMLOG_READQ(einfo) (&((einfo)->read_q))