/**************************************************************************** * drivers/can.c * * Copyright (C) 2008-2009, 2011-2012, 2014-2015 Gregory Nutt. All rights reserved. * Author: Gregory Nutt * * Redistribution and use in source and binary forms, with or without * modification, are permitted provided that the following conditions * are met: * * 1. Redistributions of source code must retain the above copyright * notice, this list of conditions and the following disclaimer. * 2. Redistributions in binary form must reproduce the above copyright * notice, this list of conditions and the following disclaimer in * the documentation and/or other materials provided with the * distribution. * 3. Neither the name NuttX nor the names of its contributors may be * used to endorse or promote products derived from this software * without specific prior written permission. * * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE * COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS * OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED * AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN * ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE * POSSIBILITY OF SUCH DAMAGE. * ****************************************************************************/ /**************************************************************************** * Included Files ****************************************************************************/ #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #ifdef CONFIG_CAN /**************************************************************************** * Pre-processor Definitions ****************************************************************************/ /* Debug ********************************************************************/ /* Non-standard debug that may be enabled just for testing CAN */ #ifdef CONFIG_DEBUG_CAN # define candbg dbg # define canvdbg vdbg # define canlldbg lldbg # define canllvdbg llvdbg #else # define candbg(x...) # define canvdbg(x...) # define canlldbg(x...) # define canllvdbg(x...) #endif /* Timing Definitions *******************************************************/ #define HALF_SECOND_MSEC 500 #define HALF_SECOND_USEC 500000L /**************************************************************************** * Private Type Definitions ****************************************************************************/ /**************************************************************************** * Private Function Prototypes ****************************************************************************/ /* CAN helpers */ static uint8_t can_dlc2bytes(uint8_t dlc); #if 0 /* Not used */ static uint8_t can_bytes2dlc(uint8_t nbytes); #endif /* Character driver methods */ static int can_open(FAR struct file *filep); static int can_close(FAR struct file *filep); static ssize_t can_read(FAR struct file *filep, FAR char *buffer, size_t buflen); static int can_xmit(FAR struct can_dev_s *dev); static ssize_t can_write(FAR struct file *filep, FAR const char *buffer, size_t buflen); static inline ssize_t can_rtrread(FAR struct can_dev_s *dev, FAR struct canioc_rtr_s *rtr); static int can_ioctl(FAR struct file *filep, int cmd, unsigned long arg); /**************************************************************************** * Private Data ****************************************************************************/ static const struct file_operations g_canops = { can_open, /* open */ can_close, /* close */ can_read, /* read */ can_write, /* write */ 0, /* seek */ can_ioctl /* ioctl */ #ifndef CONFIG_DISABLE_POLL , 0 /* poll */ #endif #ifndef CONFIG_DISABLE_PSEUDOFS_OPERATIONS , 0 /* unlink */ #endif }; /**************************************************************************** * Private Functions ****************************************************************************/ /**************************************************************************** * Name: can_dlc2bytes * * Description: * In the CAN FD format, the coding of the DLC differs from the standard * CAN format. The DLC codes 0 to 8 have the same coding as in standard * CAN. But the codes 9 to 15 all imply a data field of 8 bytes with * standard CAN. In CAN FD mode, the values 9 to 15 are encoded to values * in the range 12 to 64. * * Input Parameter: * dlc - the DLC value to convert to a byte count * * Returned Value: * The number of bytes corresponding to the DLC value. * ****************************************************************************/ static uint8_t can_dlc2bytes(uint8_t dlc) { if (dlc > 8) { #ifdef CONFIG_CAN_FD switch (dlc) { case 9: return 12; case 10: return 16; case 11: return 20; case 12: return 24; case 13: return 32; case 14: return 48; default: case 15: return 64; } #else return 8; #endif } return dlc; } /**************************************************************************** * Name: can_bytes2dlc * * Description: * In the CAN FD format, the coding of the DLC differs from the standard * CAN format. The DLC codes 0 to 8 have the same coding as in standard * CAN. But the codes 9 to 15 all imply a data field of 8 bytes with * standard CAN. In CAN FD mode, the values 9 to 15 are encoded to values * in the range 12 to 64. * * Input Parameter: * nbytes - the byte count to convert to a DLC value * * Returned Value: * The encoded DLC value corresponding to at least that number of bytes. * ****************************************************************************/ #if 0 /* Not used */ static uint8_t can_bytes2dlc(FAR struct sam_can_s *priv, uint8_t nbytes) { if (nbytes <= 8) { return nbytes; } #ifdef CONFIG_CAN_FD else if (nbytes <= 12) { return 9; } else if (nbytes <= 16) { return 10; } else if (nbytes <= 20) { return 11; } else if (nbytes <= 24) { return 12; } else if (nbytes <= 32) { return 13; } else if (nbytes <= 48) { return 14; } else /* if (nbytes <= 64) */ { return 15; } #else else { return 8; } #endif } #endif /**************************************************************************** * Name: can_open * * Description: * This function is called whenever the CAN device is opened. * ****************************************************************************/ static int can_open(FAR struct file *filep) { FAR struct inode *inode = filep->f_inode; FAR struct can_dev_s *dev = inode->i_private; uint8_t tmp; int ret = OK; canvdbg("ocount: %d\n", dev->cd_ocount); /* If the port is the middle of closing, wait until the close is finished */ if (sem_wait(&dev->cd_closesem) != OK) { ret = -get_errno(); } else { /* Increment the count of references to the device. If this is the first * time that the driver has been opened for this device, then initialize * the device. */ tmp = dev->cd_ocount + 1; if (tmp == 0) { /* More than 255 opens; uint8_t overflows to zero */ ret = -EMFILE; } else { /* Check if this is the first time that the driver has been opened. */ if (tmp == 1) { /* Yes.. perform one time hardware initialization. */ irqstate_t flags = irqsave(); ret = dev_setup(dev); if (ret == OK) { /* Mark the FIFOs empty */ dev->cd_xmit.tx_head = 0; dev->cd_xmit.tx_queue = 0; dev->cd_xmit.tx_tail = 0; dev->cd_recv.rx_head = 0; dev->cd_recv.rx_tail = 0; /* Finally, Enable the CAN RX interrupt */ dev_rxint(dev, true); /* Save the new open count only on success */ dev->cd_ocount = 1; } irqrestore(flags); } else { /* Save the incremented open count */ dev->cd_ocount = tmp; } } sem_post(&dev->cd_closesem); } return ret; } /**************************************************************************** * Name: can_close * * Description: * This routine is called when the CAN device is closed. * It waits for the last remaining data to be sent. * ****************************************************************************/ static int can_close(FAR struct file *filep) { FAR struct inode *inode = filep->f_inode; FAR struct can_dev_s *dev = inode->i_private; irqstate_t flags; int ret = OK; canvdbg("ocount: %d\n", dev->cd_ocount); if (sem_wait(&dev->cd_closesem) != OK) { ret = -get_errno(); } else { /* Decrement the references to the driver. If the reference count will * decrement to 0, then uninitialize the driver. */ if (dev->cd_ocount > 1) { dev->cd_ocount--; sem_post(&dev->cd_closesem); } else { /* There are no more references to the port */ dev->cd_ocount = 0; /* Stop accepting input */ dev_rxint(dev, false); /* Now we wait for the transmit FIFO to clear */ while (dev->cd_xmit.tx_head != dev->cd_xmit.tx_tail) { #ifndef CONFIG_DISABLE_SIGNALS usleep(HALF_SECOND_USEC); #else up_mdelay(HALF_SECOND_MSEC); #endif } /* And wait for the TX hardware FIFO to drain */ while (!dev_txempty(dev)) { #ifndef CONFIG_DISABLE_SIGNALS usleep(HALF_SECOND_USEC); #else up_mdelay(HALF_SECOND_MSEC); #endif } /* Free the IRQ and disable the CAN device */ flags = irqsave(); /* Disable interrupts */ dev_shutdown(dev); /* Disable the CAN */ irqrestore(flags); sem_post(&dev->cd_closesem); } } return ret; } /**************************************************************************** * Name: can_read * * Description: * Read standard CAN messages * ****************************************************************************/ static ssize_t can_read(FAR struct file *filep, FAR char *buffer, size_t buflen) { FAR struct inode *inode = filep->f_inode; FAR struct can_dev_s *dev = inode->i_private; size_t nread; irqstate_t flags; int ret = 0; canvdbg("buflen: %d\n", buflen); /* The caller must provide enough memory to catch the smallest possible * message. This is not a system error condition, but we won't permit * it, Hence we return 0. */ if (buflen >= CAN_MSGLEN(0)) { /* Interrupts must be disabled while accessing the cd_recv FIFO */ flags = irqsave(); while (dev->cd_recv.rx_head == dev->cd_recv.rx_tail) { /* The receive FIFO is empty -- was non-blocking mode selected? */ if (filep->f_oflags & O_NONBLOCK) { ret = -EAGAIN; goto return_with_irqdisabled; } /* Wait for a message to be received */ dev->cd_nrxwaiters++; do { ret = sem_wait(&dev->cd_recv.rx_sem); } while (ret >= 0 && dev->cd_recv.rx_head == dev->cd_recv.rx_tail); dev->cd_nrxwaiters--; if (ret < 0) { ret = -get_errno(); goto return_with_irqdisabled; } } /* The cd_recv FIFO is not empty. Copy all buffered data that will fit * in the user buffer. */ nread = 0; do { /* Will the next message in the FIFO fit into the user buffer? */ FAR struct can_msg_s *msg = &dev->cd_recv.rx_buffer[dev->cd_recv.rx_head]; int nbytes = can_dlc2bytes(msg->cm_hdr.ch_dlc); int msglen = CAN_MSGLEN(nbytes); if (nread + msglen > buflen) { break; } /* Copy the message to the user buffer */ memcpy(&buffer[nread], msg, msglen); nread += msglen; /* Increment the head of the circular message buffer */ if (++dev->cd_recv.rx_head >= CONFIG_CAN_FIFOSIZE) { dev->cd_recv.rx_head = 0; } } while (dev->cd_recv.rx_head != dev->cd_recv.rx_tail); /* All on the messages have bee transferred. Return the number of bytes * that were read. */ ret = nread; return_with_irqdisabled: irqrestore(flags); } return ret; } /**************************************************************************** * Name: can_xmit * * Description: * Send the message at the head of the cd_xmit FIFO * * Assumptions: * Called with interrupts disabled * ****************************************************************************/ static int can_xmit(FAR struct can_dev_s *dev) { int tmpndx; int ret = -EBUSY; canllvdbg("xmit head: %d queue: %d tail: %d\n", dev->cd_xmit.tx_head, dev->cd_xmit.tx_queue, dev->cd_xmit.tx_tail); /* If there is nothing to send, then just disable interrupts and return */ if (dev->cd_xmit.tx_head == dev->cd_xmit.tx_tail) { DEBUGASSERT(dev->cd_xmit.tx_queue == dev->cd_xmit.tx_head); dev_txint(dev, false); return -EIO; } /* Check if we have already queued all of the data in the TX fifo. * * tx_tail: Incremented in can_write each time a message is queued in the FIFO * tx_head: Incremented in can_txdone each time a message completes * tx_queue: Incremented each time that a message is sent to the hardware. * * Logically (ignoring buffer wrap-around): tx_head <= tx_queue <= tx_tail * tx_head == tx_queue == tx_tail means that the FIFO is empty * tx_head < tx_queue == tx_tail means that all data has been queued, but * we are still waiting for transmissions to complete. */ while (dev->cd_xmit.tx_queue != dev->cd_xmit.tx_tail && dev_txready(dev)) { /* No.. The FIFO should not be empty in this case */ DEBUGASSERT(dev->cd_xmit.tx_head != dev->cd_xmit.tx_tail); /* Increment the FIFO queue index before sending (because dev_send() * might call can_txdone()). */ tmpndx = dev->cd_xmit.tx_queue; if (++dev->cd_xmit.tx_queue >= CONFIG_CAN_FIFOSIZE) { dev->cd_xmit.tx_queue = 0; } /* Send the next message at the FIFO queue index */ ret = dev_send(dev, &dev->cd_xmit.tx_buffer[tmpndx]); if (ret != OK) { candbg("dev_send failed: %d\n", ret); break; } } /* Make sure that TX interrupts are enabled */ dev_txint(dev, true); return ret; } /**************************************************************************** * Name: can_write ****************************************************************************/ static ssize_t can_write(FAR struct file *filep, FAR const char *buffer, size_t buflen) { FAR struct inode *inode = filep->f_inode; FAR struct can_dev_s *dev = inode->i_private; FAR struct can_txfifo_s *fifo = &dev->cd_xmit; FAR struct can_msg_s *msg; bool inactive; ssize_t nsent = 0; irqstate_t flags; int nexttail; int nbytes; int msglen; int ret = 0; canvdbg("buflen: %d\n", buflen); /* Interrupts must disabled throughout the following */ flags = irqsave(); /* Check if the TX is inactive when we started. In certain race conditions, * there may be a pending interrupt to kick things back off, but we will * be sure here that there is not. That the hardware is IDLE and will * need to be kick-started. */ inactive = dev_txempty(dev); /* Add the messages to the FIFO. Ignore any trailing messages that are * shorter than the minimum. */ while ((buflen - nsent) >= CAN_MSGLEN(0)) { /* Check if adding this new message would over-run the drivers ability * to enqueue xmit data. */ nexttail = fifo->tx_tail + 1; if (nexttail >= CONFIG_CAN_FIFOSIZE) { nexttail = 0; } /* If the XMIT FIFO becomes full, then wait for space to become available */ while (nexttail == fifo->tx_head) { /* The transmit FIFO is full -- was non-blocking mode selected? */ if ((filep->f_oflags & O_NONBLOCK) != 0) { if (nsent == 0) { ret = -EAGAIN; } else { ret = nsent; } goto return_with_irqdisabled; } /* If the TX hardware was inactive when we started, then we will have * start the XMIT sequence generate the TX done interrupts needed * to clear the FIFO. */ if (inactive) { can_xmit(dev); } /* Wait for a message to be sent */ do { DEBUGASSERT(dev->cd_ntxwaiters < 255); dev->cd_ntxwaiters++; ret = sem_wait(&fifo->tx_sem); dev->cd_ntxwaiters--; if (ret < 0 && get_errno() != EINTR) { ret = -get_errno(); goto return_with_irqdisabled; } } while (ret < 0); /* Re-check the FIFO state */ inactive = dev_txempty(dev); } /* We get here if there is space at the end of the FIFO. Add the new * CAN message at the tail of the FIFO. */ msg = (FAR struct can_msg_s *)&buffer[nsent]; nbytes = can_dlc2bytes(msg->cm_hdr.ch_dlc); msglen = CAN_MSGLEN(nbytes); memcpy(&fifo->tx_buffer[fifo->tx_tail], msg, msglen); /* Increment the tail of the circular buffer */ fifo->tx_tail = nexttail; /* Increment the number of bytes that were sent */ nsent += msglen; } /* We get here after all messages have been added to the FIFO. Check if * we need to kick of the XMIT sequence. */ if (inactive) { can_xmit(dev); } /* Return the number of bytes that were sent */ ret = nsent; return_with_irqdisabled: irqrestore(flags); return ret; } /**************************************************************************** * Name: can_rtrread * * Description: * Read RTR messages. The RTR message is a special message -- it is an * outgoing message that says "Please re-transmit the message with the * same identifier as this message. So the RTR read is really a * send-wait-receive operation. * ****************************************************************************/ static inline ssize_t can_rtrread(FAR struct can_dev_s *dev, FAR struct canioc_rtr_s *rtr) { FAR struct can_rtrwait_s *wait = NULL; irqstate_t flags; int i; int ret = -ENOMEM; /* Disable interrupts through this operation */ flags = irqsave(); /* Find an available slot in the pending RTR list */ for (i = 0; i < CONFIG_CAN_NPENDINGRTR; i++) { FAR struct can_rtrwait_s *tmp = &dev->cd_rtr[i]; if (!rtr->ci_msg) { tmp->cr_id = rtr->ci_id; tmp->cr_msg = rtr->ci_msg; dev->cd_npendrtr++; wait = tmp; break; } } if (wait) { /* Send the remote transmission request */ ret = dev_remoterequest(dev, wait->cr_id); if (ret == OK) { /* Then wait for the response */ ret = sem_wait(&wait->cr_sem); } } irqrestore(flags); return ret; } /**************************************************************************** * Name: can_ioctl ****************************************************************************/ static int can_ioctl(FAR struct file *filep, int cmd, unsigned long arg) { FAR struct inode *inode = filep->f_inode; FAR struct can_dev_s *dev = inode->i_private; int ret = OK; canvdbg("cmd: %d arg: %ld\n", cmd, arg); /* Handle built-in ioctl commands */ switch (cmd) { /* CANIOC_RTR: Send the remote transmission request and wait for the * response. Argument is a reference to struct canioc_rtr_s * (casting to uintptr_t first eliminates complaints on some * architectures where the sizeof long is different from the size of * a pointer). */ case CANIOC_RTR: ret = can_rtrread(dev, (FAR struct canioc_rtr_s *)((uintptr_t)arg)); break; /* Not a "built-in" ioctl command.. perhaps it is unique to this * lower-half, device driver. */ default: ret = dev_ioctl(dev, cmd, arg); break; } return ret; } /**************************************************************************** * Public Functions ****************************************************************************/ /**************************************************************************** * Name: can_register * * Description: * Register serial console and serial ports. * ****************************************************************************/ int can_register(FAR const char *path, FAR struct can_dev_s *dev) { int i; /* Initialize the CAN device structure */ dev->cd_ocount = 0; dev->cd_ntxwaiters = 0; dev->cd_nrxwaiters = 0; dev->cd_npendrtr = 0; sem_init(&dev->cd_xmit.tx_sem, 0, 0); sem_init(&dev->cd_recv.rx_sem, 0, 0); sem_init(&dev->cd_closesem, 0, 1); for (i = 0; i < CONFIG_CAN_NPENDINGRTR; i++) { sem_init(&dev->cd_rtr[i].cr_sem, 0, 0); dev->cd_rtr[i].cr_msg = NULL; } /* Initialize/reset the CAN hardware */ dev_reset(dev); /* Register the CAN device */ canvdbg("Registering %s\n", path); return register_driver(path, &g_canops, 0666, dev); } /**************************************************************************** * Name: can_receive * * Description: * Called from the CAN interrupt handler when new read data is available * * Input Parameters: * dev - CAN driver state structure * hdr - CAN message header * data - CAN message data (if DLC > 0) * * Returned Value: * OK on success; a negated errno on failure. * * Assumptions: * CAN interrupts are disabled. * ****************************************************************************/ int can_receive(FAR struct can_dev_s *dev, FAR struct can_hdr_s *hdr, FAR uint8_t *data) { FAR struct can_rxfifo_s *fifo = &dev->cd_recv; FAR uint8_t *dest; int nexttail; int err = -ENOMEM; int i; canllvdbg("ID: %d DLC: %d\n", hdr->ch_id, hdr->ch_dlc); /* Check if adding this new message would over-run the drivers ability to * enqueue read data. */ nexttail = fifo->rx_tail + 1; if (nexttail >= CONFIG_CAN_FIFOSIZE) { nexttail = 0; } /* First, check if this response matches any RTR response that we may be * waiting for. */ if (dev->cd_npendrtr > 0) { /* There are pending RTR requests -- search the lists of requests * and see any any matches this new message. */ for (i = 0; i < CONFIG_CAN_NPENDINGRTR; i++) { FAR struct can_rtrwait_s *rtr = &dev->cd_rtr[i]; FAR struct can_msg_s *msg = rtr->cr_msg; /* Check if the entry is valid and if the ID matches. A valid * entry has a non-NULL receiving address */ if (msg && hdr->ch_id == rtr->cr_id) { int nbytes; /* We have the response... copy the data to the user's buffer */ memcpy(&msg->cm_hdr, hdr, sizeof(struct can_hdr_s)); nbytes = can_dlc2bytes(hdr->ch_dlc); for (i = 0, dest = msg->cm_data; i < nbytes; i++) { *dest++ = *data++; } /* Mark the entry unused */ rtr->cr_msg = NULL; dev->cd_npendrtr--; /* And restart the waiting thread */ sem_post(&rtr->cr_sem); } } } /* Refuse the new data if the FIFO is full */ if (nexttail != fifo->rx_head) { int nbytes; /* Add the new, decoded CAN message at the tail of the FIFO. * * REVISIT: In the CAN FD format, the coding of the DLC differs from * the standard CAN format. The DLC codes 0 to 8 have the same coding * as in standard CAN, the codes 9 to 15, which in standard CAN all * code a data field of 8 bytes, are encoded: * * 9->12, 10->16, 11->20, 12->24, 13->32, 14->48, 15->64 */ memcpy(&fifo->rx_buffer[fifo->rx_tail].cm_hdr, hdr, sizeof(struct can_hdr_s)); nbytes = can_dlc2bytes(hdr->ch_dlc); for (i = 0, dest = fifo->rx_buffer[fifo->rx_tail].cm_data; i < nbytes; i++) { *dest++ = *data++; } /* Increment the tail of the circular buffer */ fifo->rx_tail = nexttail; /* The increment the counting semaphore. The maximum value should be * CONFIG_CAN_FIFOSIZE -- one possible count for each allocated * message buffer. */ if (dev->cd_nrxwaiters > 0) { sem_post(&fifo->rx_sem); } err = OK; } return err; } /**************************************************************************** * Name: can_txdone * * Description: * Called when the hardware has processed the outgoing TX message. This * normally means that the CAN messages was sent out on the wire. But * if the CAN hardware supports a H/W TX FIFO, then this call may mean * only that the CAN message has been added to the H/W FIFO. In either * case, the upper-half CAN driver can remove the outgoing message from * the S/W FIFO and discard it. * * This function may be called in different contexts, depending upon the * nature of the underlying CAN hardware. * * 1. No H/W TX FIFO (CONFIG_CAN_TXREADY not defined) * * This function is only called from the CAN interrupt handler at the * completion of a send operation. * * can_write() -> can_xmit() -> dev_send() * CAN interrupt -> can_txdone() * * If the CAN hardware is busy, then the call to dev_send() will * fail, the S/W TX FIFO will accumulate outgoing messages, and the * thread calling can_write() may eventually block waiting for space in * the S/W TX FIFO. * * When the CAN hardware completes the transfer and processes the * CAN interrupt, the call to can_txdone() will make space in the S/W * TX FIFO and will awaken the waiting can_write() thread. * * 2a. H/W TX FIFO (CONFIG_CAN_TXREADY=y) and S/W TX FIFO not full * * This function will be called back from dev_send() immediately when a * new CAN message is added to H/W TX FIFO: * * can_write() -> can_xmit() -> dev_send() -> can_txdone() * * When the H/W TX FIFO becomes full, dev_send() will fail and * can_txdone() will not be called. In this case the S/W TX FIFO will * accumulate outgoing messages, and the thread calling can_write() may * eventually block waiting for space in the S/W TX FIFO. * * 2b. H/W TX FIFO (CONFIG_CAN_TXREADY=y) and S/W TX FIFO full * * In this case, the thread calling can_write() is blocked waiting for * space in the S/W TX FIFO. * * CAN interrupt -> can_txready() -> can_xmit() -> dev_send() -> can_txdone() * * The call dev_send() should not fail in this case and the subsequent * call to can_txdone() will make space in the S/W TX FIFO and will * awaken the waiting thread. * * Input Parameters: * dev - The specific CAN device * hdr - The 16-bit CAN header * data - An array contain the CAN data. * * Returned Value: * OK on success; a negated errno on failure. * * Assumptions: * Interrupts are disabled. This is required by can_xmit() which is called * by this function. Interrupts are explicitly disabled when called * through can_write(). Interrupts are expected be disabled when called * from the CAN interrupt handler. * ****************************************************************************/ int can_txdone(FAR struct can_dev_s *dev) { int ret = -ENOENT; canllvdbg("xmit head: %d queue: %d tail: %d\n", dev->cd_xmit.tx_head, dev->cd_xmit.tx_queue, dev->cd_xmit.tx_tail); /* Verify that the xmit FIFO is not empty */ if (dev->cd_xmit.tx_head != dev->cd_xmit.tx_tail) { /* The tx_queue index is incremented each time can_xmit() queues * the transmission. When can_txdone() is called, the tx_queue * index should always have been advanced beyond the current tx_head * index. */ DEBUGASSERT(dev->cd_xmit.tx_head != dev->cd_xmit.tx_queue); /* Remove the message at the head of the xmit FIFO */ if (++dev->cd_xmit.tx_head >= CONFIG_CAN_FIFOSIZE) { dev->cd_xmit.tx_head = 0; } /* Send the next message in the FIFO */ (void)can_xmit(dev); /* Are there any threads waiting for space in the TX FIFO? */ if (dev->cd_ntxwaiters > 0) { /* Yes.. Inform them that new xmit space is available */ ret = sem_post(&dev->cd_xmit.tx_sem); } else { ret = OK; } } return ret; } /**************************************************************************** * Name: can_txready * * Description: * Called from the CAN interrupt handler at the completion of a send * operation. This interface is needed only for CAN hardware that * supports queing of outgoing messages in a H/W FIFO. * * The CAN upper half driver also supports a queue of output messages in a * S/W FIFO. Messages are added to that queue when when can_write() is * called and removed from the queue in can_txdone() when each TX message * is complete. * * After each message is added to the S/W FIFO, the CAN upper half driver * will attempt to send the message by calling into the lower half driver. * That send will not be performed if the lower half driver is busy, i.e., * if dev_txready() returns false. In that case, the number of messages in * the S/W FIFO can grow. If the S/W FIFO becomes full, then can_write() * will wait for space in the S/W FIFO. * * If the CAN hardware does not support a H/W FIFO then busy means that * the hardware is actively sending the message and is guaranteed to * become non-busy (i.e, dev_txready()) when the send transfer completes * and can_txdone() is called. So the call to can_txdone() means that the * transfer has completed and also that the hardware is ready to accept * another transfer. * * If the CAN hardware supports a H/W FIFO, can_txdone() is not called * when the tranfer is complete, but rather when the transfer is queued in * the H/W FIFO. When the H/W FIFO becomes full, then dev_txready() will * report false and the number of queued messages in the S/W FIFO will grow. * * There is no mechanism in this case to inform the upper half driver when * the hardware is again available, when there is again space in the H/W * FIFO. can_txdone() will not be called again. If the S/W FIFO becomes * full, then the upper half driver will wait for space to become * available, but there is no event to awaken it and the driver will hang. * * Enabling this feature adds support for the can_txready() interface. * This function is called from the lower half driver's CAN interrupt * handler each time a TX transfer completes. This is a sure indication * that the H/W FIFO is no longer full. can_txready() will then awaken * the can_write() logic and the hang condition is avoided. * * Input Parameters: * dev - The specific CAN device * * Returned Value: * OK on success; a negated errno on failure. * * Assumptions: * Interrupts are disabled. This is required by can_xmit() which is called * by this function. * ****************************************************************************/ #ifdef CONFIG_CAN_TXREADY int can_txready(FAR struct can_dev_s *dev) { int ret = -ENOENT; canllvdbg("xmit head: %d queue: %d tail: %d waiters: %d\n", dev->cd_xmit.tx_head, dev->cd_xmit.tx_queue, dev->cd_xmit.tx_tail, dev->cd_ntxwaiters); /* Verify that the xmit FIFO is not empty. This is safe because interrupts * are always disabled when calling into can_xmit(); this cannot collide * with ongoing activity from can_write(). */ if (dev->cd_xmit.tx_head != dev->cd_xmit.tx_tail) { /* Send the next message in the S/W FIFO. In the case where the * H/W TX FIFO is not empty, this should add one more CAN message * to the H/W TX FIFO and can_txdone() should be called, making * space in the S/W FIFO */ (void)can_xmit(dev); /* Inform one waiter that new xmit space is available in the S/W FIFO. * NOTE that is can_txdone() is, indeed, called twice that the tx_sem * will also be posted twice. This is a little inefficient, but not * harmful. */ /* Are there any threads waiting for space in the xmit FIFO? */ if (dev->cd_ntxwaiters > 0) { ret = sem_post(&dev->cd_xmit.tx_sem); } } return ret; } #endif /* CONFIG_CAN_TXREADY */ #endif /* CONFIG_CAN */