read.c

PCM9880是一块PC/104界面的双端口隔离CAN总线通讯卡

/* read.c
 * Linux CAN-bus device driver.
 * Written by Arnaud Westenberg email:[e-mail]
 * This software is released under the GPL-License.
 * Version 0.7  6 Aug 2001
 */

#include <linux/autoconf.h>
#if defined (CONFIG_MODVERSIONS) && !defined (MODVERSIONS)
#define MODVERSIONS
#endif

#if defined (MODVERSIONS)
#include <linux/modversions.h>
#endif

#include <linux/malloc.h>
#include <linux/version.h>
#include <asm/uaccess.h>
#include <asm/irq.h>

#include "../include/main.h"
#include "../include/read.h"
#include "../include/ioctl.h"

/* This is the 'Normal' read handler for normal transmission messages */
inline ssize_t can_std_read(struct file *file, struct canfifo_t *fifo, 
			struct msgobj_t *obj, char *buffer, size_t length)
{
	int can_timeout, ret;
	int bytes_avail = 0, bytes_to_copy = 0;

	cli();
	if (fifo->rx_readp == fifo->rx_writep) {	// Buffer is empty
		if (file->f_flags & O_NONBLOCK) {
			sti();
			return -EAGAIN;
		}
		obj->ret = 0;
		can_timeout = interruptible_sleep_on_timeout(&fifo->readq,
								CANTIMEOUT);
		sti();
		if (signal_pending(current)) {
			DEBUGMSG("Rx interrupted\n");
			return -EINTR;
		}
		if (!can_timeout) {
			DEBUGMSG("Rx timeout\n");
			return -EIO;
		}
		if (obj->ret < 0)
			return obj->ret;
	}
	/* Calculate available bytes in the buffer */
	cli();
	bytes_avail = ((int)fifo->rx_readp < (int)fifo->rx_writep) ?
			((int)fifo->rx_writep - (int)fifo->rx_readp) :
			((int)fifo->rx_writep - (int)fifo->rx_readp + 
							(int)fifo->rx_size);
	sti();
		
	bytes_to_copy = (length < bytes_avail) ? length : bytes_avail;
	ret = bytes_to_copy;

	/* Copy the data to user space */
	while (bytes_to_copy > 0) {
		copy_to_user(buffer, fifo->rx_readp, sizeof(struct canmsg_t));
		buffer += sizeof(struct canmsg_t);
		bytes_to_copy -= sizeof(struct canmsg_t);
		fifo->rx_readp++;
		if (fifo->rx_readp >= fifo->buf_rx_entry + MAX_BUF_LENGTH)
			fifo->rx_readp = fifo->buf_rx_entry;
	}

	return ret;
}

/* This is the 'RTR' read handler for remote transmission request messages */
inline ssize_t can_rtr_read(struct chip_t *chip, struct msgobj_t *obj, 
								char *buffer)
{
	unsigned long flags;
	struct rtr_id *rtr_current, *new_rtr_entry;
	struct canmsg_t read_msg;
	
	DEBUGMSG("Remote transmission request\n");
	spin_lock_irqsave(&hardware_p->rtr_lock, flags);
	if (hardware_p->rtr_queue == NULL) { //No remote messages pending
		new_rtr_entry=(struct rtr_id *)kmalloc(sizeof(struct rtr_id),GFP_ATOMIC);
		if (new_rtr_entry == NULL) {
			spin_unlock_irqrestore(&hardware_p->rtr_lock, 
								flags);
			return -ENOMEM;
		}
		hardware_p->rtr_queue=new_rtr_entry;
	}
	else {
		rtr_current=hardware_p->rtr_queue;
		while (rtr_current->next != NULL)
			rtr_current=rtr_current->next;
		new_rtr_entry=(struct rtr_id *)kmalloc(sizeof(struct rtr_id),GFP_ATOMIC);
		rtr_current->next=new_rtr_entry;
	}
#if (LINUX_VERSION_CODE <= KERNEL_VERSION(2,2,19))
	init_waitqueue(&new_rtr_entry->rtr_wq);
#else
	init_waitqueue_head(&new_rtr_entry->rtr_wq);
#endif
	new_rtr_entry->id = read_msg.id;
	new_rtr_entry->rtr_message = &read_msg;
	new_rtr_entry->next=NULL;

	spin_unlock_irqrestore(&hardware_p->rtr_lock, flags);

	/* Send remote transmission request */
	chip->chipspecops->remote_request(chip,obj);
	obj->ret = 0;
	interruptible_sleep_on(&new_rtr_entry->rtr_wq);

	spin_lock_irqsave(&hardware_p->rtr_lock, flags);
	copy_to_user(buffer, &read_msg, sizeof(struct canmsg_t));
	if (hardware_p->rtr_queue == new_rtr_entry) {
		if (new_rtr_entry->next != NULL) 
			hardware_p->rtr_queue=new_rtr_entry->next;
		else
			hardware_p->rtr_queue=NULL;
	}
	else {
		rtr_current=hardware_p->rtr_queue;
		while (rtr_current->next != new_rtr_entry)
			rtr_current=rtr_current->next;
		if (new_rtr_entry->next != NULL)
			rtr_current->next=new_rtr_entry->next;
		else
			rtr_current->next=NULL;
	}
	spin_unlock_irqrestore(&hardware_p->rtr_lock, flags);
	kfree(new_rtr_entry);

	return obj->ret;
}

ssize_t can_read(struct file *file, char *buffer, size_t length, loff_t *offset)
{
	struct msgobj_t *obj;
	struct chip_t *chip;
	struct canfifo_t *fifo;
	struct canmsg_t read_msg;
	int ret=0;

	if (length < sizeof(struct canmsg_t)) {
		DEBUGMSG("Trying to read less bytes than a CAN message, \n");
		DEBUGMSG("this will always return zero.\n");
		return 0;
	}
	if (length > 8 * sizeof(struct canmsg_t)) {
		DEBUGMSG("Reading more than 8 CAN messages, this is not supported.\n");
		DEBUGMSG("Defaulting to 8 messages.\n");
		length = 8 * sizeof(struct canmsg_t);
	}
	/* Initialize hardware pointers */
	if ( (obj = objects_p[MINOR_NR]) == NULL) {
		CANMSG("Could not assign buffer structure\n");
		return -1;
	}
	if ( (chip = obj->hostchip) == NULL) {
		CANMSG("Device is not correctly configured,\n");
		CANMSG("please reload the driver.\n");
		return -1;
	}
	if ( (fifo = obj->fifo) == NULL) {
		CANMSG("Could not assign buffer memory.\n");
		return -1;
	}

	copy_from_user(&read_msg, buffer, sizeof(struct canmsg_t));
	if (read_msg.flags & MSG_RTR)
		ret = can_rtr_read(chip, obj, buffer);
	else
		ret = can_std_read(file, fifo, obj, buffer, length);

	return ret;
}