Portable and maintable HD44780 driver files.

2000-02-21 11:24:09 +00:00
parent 6cefefd52c
commit e481f1311e
12 changed files with 978 additions and 0 deletions
@@ -0,0 +1,170 @@
+/*
+ * lcd_sem.c  -- semaphore code written for lcdtime and meter to mediate
+ * access to the parallel port.
+ * 
+ * Written by Benjamin Tse (blt@mundil.cs.mu.edu.au); August,October 1995
+ * 
+ * Functions in this file:
+ *   getkey      returns the key for the semaphore
+ *   sem_get     create the semaphore (and initialise) if one doesn't exist
+ *                otherwise return its key
+ *   sem_wait    wait on the semaphore
+ *   sem_signal  signal on the semaphore
+ *   sem_remove  remove the semaphore
+ * 
+ * Legal stuff: At no stage was this program written, assembled or compiled on
+ * any computer at the University of Melbourne, Australia. This program is
+ * Copyright (C) 1995 Benjamin Tse (blt@mundil.cs.mu.oz.au) and covered by
+ * GNU's GPL. In particular, this program is free software and comes WITHOUT
+ * ANY WARRANTY.
+ * 
+ * $Id$
+ */
+
+#include <stdio.h>
+#include <stdlib.h>
+#include <sys/types.h>	/* for semaphore functions */
+#include <sys/ipc.h>
+#include <sys/sem.h>
+#include <errno.h>
+
+#include "lcd_sem.h"
+
+#define SEMAPHORE       "portctrl"
+#define SEMKEY          0x706f7274      /* semaphore key */
+#define SEMCOUNT        1               /* number of semaphores to create */
+#define WMODE           0660		/* access permissions */
+
+#define SEM_SIGNAL      0,1,SEM_UNDO
+#define SEM_WAIT        0,-1,SEM_UNDO
+
+/* functions local to this file */
+static key_t getkey(register char *p);
+ 
+/* global variables */
+static struct sembuf semaphore_wait = {SEM_WAIT};
+static struct sembuf semaphore_signal = {SEM_SIGNAL};
+
+static char rcsId[] = "$Id$";
+
+/*
+ * getkey  returns the key for the semaphore
+ */
+
+static key_t
+getkey(register char *p)
+{
+    return((key_t) SEMKEY);
+}
+
+/*
+ * create the semaphore if one doesn't exist and initialise it to 1, else 
+ * return the semaphore set id
+ */
+
+int
+sem_get(void)
+{
+    int semid;
+    union semun semval;
+
+    if ((semid = semget(getkey(SEMAPHORE), SEMCOUNT, 
+			IPC_CREAT | IPC_EXCL | WMODE)) < 0)
+    {
+	switch (errno)
+	{
+	    case EEXIST:
+	    	/* semaphore set exists, get id and return it */
+		if ((semid = semget(getkey(SEMAPHORE), SEMCOUNT,
+		    		IPC_EXCL | WMODE)) < 0)
+		{
+		    perror("semget");
+		    exit(1);
+		}
+		return semid;
+		break;
+	    case EACCES:
+	    	/* don't have permissions for semaphore, need to change key */
+		perror("semget, can't get permissions for semaphore");
+		exit(1);
+		break;
+	    default:
+		perror("semget");
+	    	exit(1);
+		break;
+	}
+    }
+    else
+    {
+	/* initialise semaphore to 1 */
+    	semval.val = 1;
+
+	if (semctl(semid, 0, SETVAL, semval) < 0)
+	{
+	    perror("setval, can't initialise semaphore");
+	    exit(1);
+	}
+    }
+								        
+    return semid;
+}
+
+/*
+ * wait on the semaphore
+ */
+
+int
+sem_wait(int sid)
+{
+    if (semop(sid, &semaphore_wait, 1) < -1)
+    {
+	perror(SEMAPHORE);
+	exit(1);
+    }
+
+    return 0;
+}
+
+/*
+ * signal on the semaphore
+ */
+
+int
+sem_signal(int sid)
+{
+    if (semop(sid, &semaphore_signal, 1) < -1)
+    {
+	perror(SEMAPHORE);
+	exit(1);
+    }
+
+    return 0;
+}
+
+/*
+ * remove the semaphore
+ */
+
+int
+sem_remove(int sid)
+{
+    int i;
+    union semun dummy;
+    
+    if ((i = semctl(sid, 0, IPC_RMID, dummy)) < 0)
+    {
+	switch(i)
+	{
+	    case EIDRM:
+	        /* semaphore removed */
+	        return 0;
+	        break;
+	    default:
+	        perror("semctl, removing semaphore");
+	        exit(1);
+	}
+    }
+
+    return 0;
+}
+