Linux Device Drivers 3 examples

1 files changed, 692 insertions, 0 deletions

diff --git a/short/short.c b/short/short.c
new file mode 100644
index 0000000..8bd39ed
--- /dev/null
+++ b/short/short.c
@@ -0,0 +1,692 @@
+/*
+ * short.c -- Simple Hardware Operations and Raw Tests
+ * short.c -- also a brief example of interrupt handling ("short int")
+ *
+ * Copyright (C) 2001 Alessandro Rubini and Jonathan Corbet
+ * Copyright (C) 2001 O'Reilly & Associates
+ *
+ * The source code in this file can be freely used, adapted,
+ * and redistributed in source or binary form, so long as an
+ * acknowledgment appears in derived source files.  The citation
+ * should list that the code comes from the book "Linux Device
+ * Drivers" by Alessandro Rubini and Jonathan Corbet, published
+ * by O'Reilly & Associates.   No warranty is attached;
+ * we cannot take responsibility for errors or fitness for use.
+ *
+ * $Id: short.c,v 1.16 2004/10/29 16:45:40 corbet Exp $
+ */
+
+/*
+ * FIXME: this driver is not safe with concurrent readers or
+ * writers.
+ */
+
+#include <linux/config.h>
+#include <linux/module.h>
+#include <linux/moduleparam.h>
+#include <linux/init.h>
+
+#include <linux/sched.h>
+#include <linux/kernel.h>	/* printk() */
+#include <linux/fs.h>		/* everything... */
+#include <linux/errno.h>	/* error codes */
+#include <linux/delay.h>	/* udelay */
+#include <linux/kdev_t.h>
+#include <linux/slab.h>
+#include <linux/mm.h>
+#include <linux/ioport.h>
+#include <linux/interrupt.h>
+#include <linux/workqueue.h>
+#include <linux/poll.h>
+#include <linux/wait.h>
+
+#include <asm/io.h>
+
+#define SHORT_NR_PORTS	8	/* use 8 ports by default */
+
+/*
+ * all of the parameters have no "short_" prefix, to save typing when
+ * specifying them at load time
+ */
+static int major = 0;	/* dynamic by default */
+module_param(major, int, 0);
+
+static int use_mem = 0;	/* default is I/O-mapped */
+module_param(use_mem, int, 0);
+
+/* default is the first printer port on PC's. "short_base" is there too
+   because it's what we want to use in the code */
+static unsigned long base = 0x378;
+unsigned long short_base = 0;
+module_param(base, long, 0);
+
+/* The interrupt line is undefined by default. "short_irq" is as above */
+static int irq = -1;
+volatile int short_irq = -1;
+module_param(irq, int, 0);
+
+static int probe = 0;	/* select at load time how to probe irq line */
+module_param(probe, int, 0);
+
+static int wq = 0;	/* select at load time whether a workqueue is used */
+module_param(wq, int, 0);
+
+static int tasklet = 0;	/* select whether a tasklet is used */
+module_param(tasklet, int, 0);
+
+static int share = 0;	/* select at load time whether install a shared irq */
+module_param(share, int, 0);
+
+MODULE_AUTHOR ("Alessandro Rubini");
+MODULE_LICENSE("Dual BSD/GPL");
+
+
+unsigned long short_buffer = 0;
+unsigned long volatile short_head;
+volatile unsigned long short_tail;
+DECLARE_WAIT_QUEUE_HEAD(short_queue);
+
+/* Set up our tasklet if we're doing that. */
+void short_do_tasklet(unsigned long);
+DECLARE_TASKLET(short_tasklet, short_do_tasklet, 0);
+
+/*
+ * Atomicly increment an index into short_buffer
+ */
+static inline void short_incr_bp(volatile unsigned long *index, int delta)
+{
+	unsigned long new = *index + delta;
+	barrier();  /* Don't optimize these two together */
+	*index = (new >= (short_buffer + PAGE_SIZE)) ? short_buffer : new;
+}
+
+
+/*
+ * The devices with low minor numbers write/read burst of data to/from
+ * specific I/O ports (by default the parallel ones).
+ * 
+ * The device with 128 as minor number returns ascii strings telling
+ * when interrupts have been received. Writing to the device toggles
+ * 00/FF on the parallel data lines. If there is a loopback wire, this
+ * generates interrupts.  
+ */
+
+int short_open (struct inode *inode, struct file *filp)
+{
+	extern struct file_operations short_i_fops;
+
+	if (iminor (inode) & 0x80)
+		filp->f_op = &short_i_fops; /* the interrupt-driven node */
+	return 0;
+}
+
+
+int short_release (struct inode *inode, struct file *filp)
+{
+	return 0;
+}
+
+
+/* first, the port-oriented device */
+
+enum short_modes {SHORT_DEFAULT=0, SHORT_PAUSE, SHORT_STRING, SHORT_MEMORY};
+
+ssize_t do_short_read (struct inode *inode, struct file *filp, char __user *buf,
+		size_t count, loff_t *f_pos)
+{
+	int retval = count, minor = iminor (inode);
+	unsigned long port = short_base + (minor&0x0f);
+	void *address = (void *) short_base + (minor&0x0f);
+	int mode = (minor&0x70) >> 4;
+	unsigned char *kbuf = kmalloc(count, GFP_KERNEL), *ptr;
+    
+	if (!kbuf)
+		return -ENOMEM;
+	ptr = kbuf;
+
+	if (use_mem)
+		mode = SHORT_MEMORY;
+	
+	switch(mode) {
+	    case SHORT_STRING:
+		insb(port, ptr, count);
+		rmb();
+		break;
+
+	    case SHORT_DEFAULT:
+		while (count--) {
+			*(ptr++) = inb(port);
+			rmb();
+		}
+		break;
+
+	    case SHORT_MEMORY:
+		while (count--) {
+			*ptr++ = ioread8(address);
+			rmb();
+		}
+		break;
+	    case SHORT_PAUSE:
+		while (count--) {
+			*(ptr++) = inb_p(port);
+			rmb();
+		}
+		break;
+
+	    default: /* no more modes defined by now */
+		retval = -EINVAL;
+		break;
+	}
+	if ((retval > 0) && copy_to_user(buf, kbuf, retval))
+		retval = -EFAULT;
+	kfree(kbuf);
+	return retval;
+}
+
+
+/*
+ * Version-specific methods for the fops structure.  FIXME don't need anymore.
+ */
+ssize_t short_read(struct file *filp, char __user *buf, size_t count, loff_t *f_pos)
+{
+	return do_short_read(filp->f_dentry->d_inode, filp, buf, count, f_pos);
+}
+
+
+
+ssize_t do_short_write (struct inode *inode, struct file *filp, const char __user *buf,
+		size_t count, loff_t *f_pos)
+{
+	int retval = count, minor = iminor(inode);
+	unsigned long port = short_base + (minor&0x0f);
+	void *address = (void *) short_base + (minor&0x0f);
+	int mode = (minor&0x70) >> 4;
+	unsigned char *kbuf = kmalloc(count, GFP_KERNEL), *ptr;
+
+	if (!kbuf)
+		return -ENOMEM;
+	if (copy_from_user(kbuf, buf, count))
+		return -EFAULT;
+	ptr = kbuf;
+
+	if (use_mem)
+		mode = SHORT_MEMORY;
+
+	switch(mode) {
+	case SHORT_PAUSE:
+		while (count--) {
+			outb_p(*(ptr++), port);
+			wmb();
+		}
+		break;
+
+	case SHORT_STRING:
+		outsb(port, ptr, count);
+		wmb();
+		break;
+
+	case SHORT_DEFAULT:
+		while (count--) {
+			outb(*(ptr++), port);
+			wmb();
+		}
+		break;
+
+	case SHORT_MEMORY:
+		while (count--) {
+			iowrite8(*ptr++, address);
+			wmb();
+		}
+		break;
+
+	default: /* no more modes defined by now */
+		retval = -EINVAL;
+		break;
+	}
+	kfree(kbuf);
+	return retval;
+}
+
+
+ssize_t short_write(struct file *filp, const char __user *buf, size_t count,
+		loff_t *f_pos)
+{
+	return do_short_write(filp->f_dentry->d_inode, filp, buf, count, f_pos);
+}
+
+
+
+
+unsigned int short_poll(struct file *filp, poll_table *wait)
+{
+	return POLLIN | POLLRDNORM | POLLOUT | POLLWRNORM;
+}
+
+
+
+
+
+
+struct file_operations short_fops = {
+	.owner	 = THIS_MODULE,
+	.read	 = short_read,
+	.write	 = short_write,
+	.poll	 = short_poll,
+	.open	 = short_open,
+	.release = short_release,
+};
+
+/* then,  the interrupt-related device */
+
+ssize_t short_i_read (struct file *filp, char __user *buf, size_t count, loff_t *f_pos)
+{
+	int count0;
+	DEFINE_WAIT(wait);
+
+	while (short_head == short_tail) {
+		prepare_to_wait(&short_queue, &wait, TASK_INTERRUPTIBLE);
+		if (short_head == short_tail)
+			schedule();
+		finish_wait(&short_queue, &wait);
+		if (signal_pending (current))  /* a signal arrived */
+			return -ERESTARTSYS; /* tell the fs layer to handle it */
+	} 
+	/* count0 is the number of readable data bytes */
+	count0 = short_head - short_tail;
+	if (count0 < 0) /* wrapped */
+		count0 = short_buffer + PAGE_SIZE - short_tail;
+	if (count0 < count) count = count0;
+
+	if (copy_to_user(buf, (char *)short_tail, count))
+		return -EFAULT;
+	short_incr_bp (&short_tail, count);
+	return count;
+}
+
+ssize_t short_i_write (struct file *filp, const char __user *buf, size_t count,
+		loff_t *f_pos)
+{
+	int written = 0, odd = *f_pos & 1;
+	unsigned long port = short_base; /* output to the parallel data latch */
+	void *address = (void *) short_base;
+
+	if (use_mem) {
+		while (written < count)
+			iowrite8(0xff * ((++written + odd) & 1), address);
+	} else {
+		while (written < count)
+			outb(0xff * ((++written + odd) & 1), port);
+	}
+
+	*f_pos += count;
+	return written;
+}
+
+
+
+
+struct file_operations short_i_fops = {
+	.owner	 = THIS_MODULE,
+	.read	 = short_i_read,
+	.write	 = short_i_write,
+	.open	 = short_open,
+	.release = short_release,
+};
+
+irqreturn_t short_interrupt(int irq, void *dev_id, struct pt_regs *regs)
+{
+	struct timeval tv;
+	int written;
+
+	do_gettimeofday(&tv);
+
+	    /* Write a 16 byte record. Assume PAGE_SIZE is a multiple of 16 */
+	written = sprintf((char *)short_head,"%08u.%06u\n",
+			(int)(tv.tv_sec % 100000000), (int)(tv.tv_usec));
+	BUG_ON(written != 16);
+	short_incr_bp(&short_head, written);
+	wake_up_interruptible(&short_queue); /* awake any reading process */
+	return IRQ_HANDLED;
+}
+
+/*
+ * The following two functions are equivalent to the previous one,
+ * but split in top and bottom half. First, a few needed variables
+ */
+
+#define NR_TIMEVAL 512 /* length of the array of time values */
+
+struct timeval tv_data[NR_TIMEVAL]; /* too lazy to allocate it */
+volatile struct timeval *tv_head=tv_data;
+volatile struct timeval *tv_tail=tv_data;
+
+static struct work_struct short_wq;
+
+
+int short_wq_count = 0;
+
+/*
+ * Increment a circular buffer pointer in a way that nobody sees
+ * an intermediate value.
+ */
+static inline void short_incr_tv(volatile struct timeval **tvp)
+{
+	if (*tvp == (tv_data + NR_TIMEVAL - 1))
+		*tvp = tv_data;	 /* Wrap */
+	else
+		(*tvp)++;
+}
+
+
+
+void short_do_tasklet (unsigned long unused)
+{
+	int savecount = short_wq_count, written;
+	short_wq_count = 0; /* we have already been removed from the queue */
+	/*
+	 * The bottom half reads the tv array, filled by the top half,
+	 * and prints it to the circular text buffer, which is then consumed
+	 * by reading processes
+	 */
+
+	/* First write the number of interrupts that occurred before this bh */
+	written = sprintf((char *)short_head,"bh after %6i\n",savecount);
+	short_incr_bp(&short_head, written);
+
+	/*
+	 * Then, write the time values. Write exactly 16 bytes at a time,
+	 * so it aligns with PAGE_SIZE
+	 */
+
+	do {
+		written = sprintf((char *)short_head,"%08u.%06u\n",
+				(int)(tv_tail->tv_sec % 100000000),
+				(int)(tv_tail->tv_usec));
+		short_incr_bp(&short_head, written);
+		short_incr_tv(&tv_tail);
+	} while (tv_tail != tv_head);
+
+	wake_up_interruptible(&short_queue); /* awake any reading process */
+}
+
+
+irqreturn_t short_wq_interrupt(int irq, void *dev_id, struct pt_regs *regs)
+{
+	/* Grab the current time information. */
+	do_gettimeofday((struct timeval *) tv_head);
+	short_incr_tv(&tv_head);
+
+	/* Queue the bh. Don't worry about multiple enqueueing */
+	schedule_work(&short_wq);
+
+	short_wq_count++; /* record that an interrupt arrived */
+	return IRQ_HANDLED;
+}
+
+
+/*
+ * Tasklet top half
+ */
+
+irqreturn_t short_tl_interrupt(int irq, void *dev_id, struct pt_regs *regs)
+{
+	do_gettimeofday((struct timeval *) tv_head); /* cast to stop 'volatile' warning */
+	short_incr_tv(&tv_head);
+	tasklet_schedule(&short_tasklet);
+	short_wq_count++; /* record that an interrupt arrived */
+	return IRQ_HANDLED;
+}
+
+
+
+
+irqreturn_t short_sh_interrupt(int irq, void *dev_id, struct pt_regs *regs)
+{
+	int value, written;
+	struct timeval tv;
+
+	/* If it wasn't short, return immediately */
+	value = inb(short_base);
+	if (!(value & 0x80))
+		return IRQ_NONE;
+	
+	/* clear the interrupting bit */
+	outb(value & 0x7F, short_base);
+
+	/* the rest is unchanged */
+
+	do_gettimeofday(&tv);
+	written = sprintf((char *)short_head,"%08u.%06u\n",
+			(int)(tv.tv_sec % 100000000), (int)(tv.tv_usec));
+	short_incr_bp(&short_head, written);
+	wake_up_interruptible(&short_queue); /* awake any reading process */
+	return IRQ_HANDLED;
+}
+
+void short_kernelprobe(void)
+{
+	int count = 0;
+	do {
+		unsigned long mask;
+
+		mask = probe_irq_on();
+		outb_p(0x10,short_base+2); /* enable reporting */
+		outb_p(0x00,short_base);   /* clear the bit */
+		outb_p(0xFF,short_base);   /* set the bit: interrupt! */
+		outb_p(0x00,short_base+2); /* disable reporting */
+		udelay(5);  /* give it some time */
+		short_irq = probe_irq_off(mask);
+
+		if (short_irq == 0) { /* none of them? */
+			printk(KERN_INFO "short: no irq reported by probe\n");
+			short_irq = -1;
+		}
+		/*
+		 * if more than one line has been activated, the result is
+		 * negative. We should service the interrupt (no need for lpt port)
+		 * and loop over again. Loop at most five times, then give up
+		 */
+	} while (short_irq < 0 && count++ < 5);
+	if (short_irq < 0)
+		printk("short: probe failed %i times, giving up\n", count);
+}
+
+irqreturn_t short_probing(int irq, void *dev_id, struct pt_regs *regs)
+{
+	if (short_irq == 0) short_irq = irq;	/* found */
+	if (short_irq != irq) short_irq = -irq; /* ambiguous */
+	return IRQ_HANDLED;
+}
+
+void short_selfprobe(void)
+{
+	int trials[] = {3, 5, 7, 9, 0};
+	int tried[]  = {0, 0, 0, 0, 0};
+	int i, count = 0;
+
+	/*
+	 * install the probing handler for all possible lines. Remember
+	 * the result (0 for success, or -EBUSY) in order to only free
+	 * what has been acquired
+      */
+	for (i = 0; trials[i]; i++)
+		tried[i] = request_irq(trials[i], short_probing,
+				SA_INTERRUPT, "short probe", NULL);
+
+	do {
+		short_irq = 0; /* none got, yet */
+		outb_p(0x10,short_base+2); /* enable */
+		outb_p(0x00,short_base);
+		outb_p(0xFF,short_base); /* toggle the bit */
+		outb_p(0x00,short_base+2); /* disable */
+		udelay(5);  /* give it some time */
+
+		/* the value has been set by the handler */
+		if (short_irq == 0) { /* none of them? */
+			printk(KERN_INFO "short: no irq reported by probe\n");
+		}
+		/*
+		 * If more than one line has been activated, the result is
+		 * negative. We should service the interrupt (but the lpt port
+		 * doesn't need it) and loop over again. Do it at most 5 times
+		 */
+	} while (short_irq <=0 && count++ < 5);
+
+	/* end of loop, uninstall the handler */
+	for (i = 0; trials[i]; i++)
+		if (tried[i] == 0)
+			free_irq(trials[i], NULL);
+
+	if (short_irq < 0)
+		printk("short: probe failed %i times, giving up\n", count);
+}
+
+
+
+/* Finally, init and cleanup */
+
+int short_init(void)
+{
+	int result;
+
+	/*
+	 * first, sort out the base/short_base ambiguity: we'd better
+	 * use short_base in the code, for clarity, but allow setting
+	 * just "base" at load time. Same for "irq".
+	 */
+	short_base = base;
+	short_irq = irq;
+
+	/* Get our needed resources. */
+	if (!use_mem) {
+		if (! request_region(short_base, SHORT_NR_PORTS, "short")) {
+			printk(KERN_INFO "short: can't get I/O port address 0x%lx\n",
+					short_base);
+			return -ENODEV;
+		}
+
+	} else {
+		if (! request_mem_region(short_base, SHORT_NR_PORTS, "short")) {
+			printk(KERN_INFO "short: can't get I/O mem address 0x%lx\n",
+					short_base);
+			return -ENODEV;
+		}
+
+		/* also, ioremap it */
+		short_base = (unsigned long) ioremap(short_base, SHORT_NR_PORTS);
+		/* Hmm... we should check the return value */
+	}
+	/* Here we register our device - should not fail thereafter */
+	result = register_chrdev(major, "short", &short_fops);
+	if (result < 0) {
+		printk(KERN_INFO "short: can't get major number\n");
+		release_region(short_base,SHORT_NR_PORTS);  /* FIXME - use-mem case? */
+		return result;
+	}
+	if (major == 0) major = result; /* dynamic */
+
+	short_buffer = __get_free_pages(GFP_KERNEL,0); /* never fails */  /* FIXME */
+	short_head = short_tail = short_buffer;
+
+	/*
+	 * Fill the workqueue structure, used for the bottom half handler.
+	 * The cast is there to prevent warnings about the type of the
+	 * (unused) argument.
+	 */
+	/* this line is in short_init() */
+	INIT_WORK(&short_wq, (void (*)(void *)) short_do_tasklet, NULL);
+
+	/*
+	 * Now we deal with the interrupt: either kernel-based
+	 * autodetection, DIY detection or default number
+	 */
+
+	if (short_irq < 0 && probe == 1)
+		short_kernelprobe();
+
+	if (short_irq < 0 && probe == 2)
+		short_selfprobe();
+
+	if (short_irq < 0) /* not yet specified: force the default on */
+		switch(short_base) {
+		    case 0x378: short_irq = 7; break;
+		    case 0x278: short_irq = 2; break;
+		    case 0x3bc: short_irq = 5; break;
+		}
+
+	/*
+	 * If shared has been specified, installed the shared handler
+	 * instead of the normal one. Do it first, before a -EBUSY will
+	 * force short_irq to -1.
+	 */
+	if (short_irq >= 0 && share > 0) {
+		result = request_irq(short_irq, short_sh_interrupt,
+				SA_SHIRQ | SA_INTERRUPT,"short",
+				short_sh_interrupt);
+		if (result) {
+			printk(KERN_INFO "short: can't get assigned irq %i\n", short_irq);
+			short_irq = -1;
+		}
+		else { /* actually enable it -- assume this *is* a parallel port */
+			outb(0x10, short_base+2);
+		}
+		return 0; /* the rest of the function only installs handlers */
+	}
+
+	if (short_irq >= 0) {
+		result = request_irq(short_irq, short_interrupt,
+				SA_INTERRUPT, "short", NULL);
+		if (result) {
+			printk(KERN_INFO "short: can't get assigned irq %i\n",
+					short_irq);
+			short_irq = -1;
+		}
+		else { /* actually enable it -- assume this *is* a parallel port */
+			outb(0x10,short_base+2);
+		}
+	}
+
+	/*
+	 * Ok, now change the interrupt handler if using top/bottom halves
+	 * has been requested
+	 */
+	if (short_irq >= 0 && (wq + tasklet) > 0) {
+		free_irq(short_irq,NULL);
+		result = request_irq(short_irq,
+				tasklet ? short_tl_interrupt :
+				short_wq_interrupt,
+				SA_INTERRUPT,"short-bh", NULL);
+		if (result) {
+			printk(KERN_INFO "short-bh: can't get assigned irq %i\n",
+					short_irq);
+			short_irq = -1;
+		}
+	}
+
+	return 0;
+}
+
+void short_cleanup(void)
+{
+	if (short_irq >= 0) {
+		outb(0x0, short_base + 2);   /* disable the interrupt */
+		if (!share) free_irq(short_irq, NULL);
+		else free_irq(short_irq, short_sh_interrupt);
+	}
+	/* Make sure we don't leave work queue/tasklet functions running */
+	if (tasklet)
+		tasklet_disable(&short_tasklet);
+	else
+		flush_scheduled_work();
+	unregister_chrdev(major, "short");
+	if (use_mem) {
+		iounmap((void __iomem *)short_base);
+		release_mem_region(short_base, SHORT_NR_PORTS);
+	} else {
+		release_region(short_base,SHORT_NR_PORTS);
+	}
+	if (short_buffer) free_page(short_buffer);
+}
+
+module_init(short_init);
+module_exit(short_cleanup);