/* * can_read - can4linux CAN driver module * * can4linux -- LINUX CAN device driver source * * This file is subject to the terms and conditions of the GNU General Public * License.  See the file "COPYING" in the main directory of this archive * for more details. * * Copyright (c) 2001 port GmbH Halle/Saale * (c) 2001 Heinz-J黵gen Oertel (oe@port.de) *          Claus Schroeter (clausi@chemie.fu-berlin.de) *------------------------------------------------------------------ * $Header: /z2/cvsroot/products/0530/software/can4linux/src/read.c,v 1.4 2008/11/23 12:05:30 oe Exp $ * *-------------------------------------------------------------------------- * * * *-------------------------------------------------------------------------- *//*** \file read.c* \author Heinz-J黵gen Oertel, port GmbH* $Revision: 1.4 $* $Date: 2008/11/23 12:05:30 $** Module Description * see Doxygen Doc for all possibilities****//* header of standard C - libraries *//* header of common types *//* shared common header *//* header of project specific types *//* project headers */#include "defs.h"/* local header *//* constant definitions---------------------------------------------------------------------------*//* local defined data types---------------------------------------------------------------------------*//* list of external used functions, if not in headers---------------------------------------------------------------------------*//* list of global defined functions---------------------------------------------------------------------------*//* list of local defined functions---------------------------------------------------------------------------*//* external variables---------------------------------------------------------------------------*//* global variables---------------------------------------------------------------------------*//* local defined variables---------------------------------------------------------------------------*//* static char _rcsid[] = "$Id: read.c,v 1.4 2008/11/23 12:05:30 oe Exp $"; *//***************************************************************************//**** \brief ssize_t read(int fd, void *buf, size_t count);* the read system call* \param fd The descriptor to read from.* \param buf The destination data buffer (array of CAN canmsg_t).* \param count The number of bytes to read.** read() attempts to read up to \a count CAN messages * (\b not \b bytes! ) from file descriptor fd* into the buffer starting at buf.* buf must be large enough to hold count times the size of * one CAN message structure \b canmsg_t.* * \codeint got;canmsg_t rx[80];			// receive buffer for read()    got = read(can_fd, rx , 80 );    if( got > 0) {      ...    } else {	// read returned with error	fprintf(stderr, "- Received got = %d\n", got);	fflush(stderr);    }* \endcode** \par ERRORS** the following errors can occur** \arg \c EINVAL \b buf points not to an large enough area,** \returns* On success, the number of CAN messages read is returned* (zero indicates end of file).* It is not an  error if this number is* smaller than the number of messages requested;* this may happen for example* because fewer messages are actually available right now,* or because read() was interrupted by a signal.* On error, -1 is returned, and errno is set  appropriately.** \internal*/__LDDK_READ_TYPE can_read( __LDDK_READ_PARAM ){size_t written = 0;unsigned long _cnt;		/* return value of copy_*_user */ unsigned int minor = __LDDK_MINOR;int blocking;int rx_fifoindex =	((struct _instance_data *)(file->private_data))->rx_index;/* msg_fifo_t *RxFifo = &Rx_Buf[minor][0]; */msg_fifo_t *RxFifo = &Rx_Buf[minor][rx_fifoindex];canmsg_t *addr;   DBGin();	/* printk(KERN_INFO " : reading in fifo[%d][%d]\n", minor, rx_fifoindex); */	addr = (canmsg_t *)buffer;	blocking = !(file->f_flags & O_NONBLOCK);		if( !access_ok( VERIFY_WRITE, buffer, count * sizeof(canmsg_t) )) {	   DBGout();	   return -EINVAL;	}	/* while( written < count && RxFifo->status == BUF_OK )  */	while( written < count ) {	    /* Look if there are currently messages in the rx queue */	    if( RxFifo->tail == RxFifo->head ) {		RxFifo->status = BUF_EMPTY;		if(blocking) {		    /* printk("empty and blocking, %d = %d\n", */			/* RxFifo->tail , RxFifo->head ); */#if 0		    if(wait_event_interruptible(CanWait[minor], \			RxFifo->tail != RxFifo->head ))		    if(wait_event_interruptible(CanWait[minor][rx_fifoindex], \			RxFifo->tail != RxFifo->head ))#else		    if(wait_event_interruptible(CanWait[minor][rx_fifoindex], \			RxFifo->tail != RxFifo->head ))#endif			return -ERESTARTSYS;		} else 		    break;	    }		    /* copy one message to the user process */	     __lddk_copy_to_user( (canmsg_t *) &(addr[written]),			(canmsg_t *) &(RxFifo->data[RxFifo->tail]),			sizeof(canmsg_t) );	    written++;	    RxFifo->tail = ++(RxFifo->tail) % MAX_BUFSIZE;	}    DBGout();    return(written);}