/**************************************************************************** * drivers/syslog/ramlog.c * * Licensed to the Apache Software Foundation (ASF) under one or more * contributor license agreements. See the NOTICE file distributed with * this work for additional information regarding copyright ownership. The * ASF licenses this file to you under the Apache License, Version 2.0 (the * "License"); you may not use this file except in compliance with the * License. You may obtain a copy of the License at * * http://www.apache.org/licenses/LICENSE-2.0 * * Unless required by applicable law or agreed to in writing, software * distributed under the License is distributed on an "AS IS" BASIS, WITHOUT * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the * License for the specific language governing permissions and limitations * under the License. * ****************************************************************************/ /**************************************************************************** * Included Files ****************************************************************************/ #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #ifdef CONFIG_RAMLOG /**************************************************************************** * Private Types ****************************************************************************/ struct ramlog_dev_s { #ifndef CONFIG_RAMLOG_NONBLOCKING volatile uint8_t rl_nwaiters; /* Number of threads waiting for data */ #endif volatile uint16_t rl_head; /* The head index (where data is added) */ volatile uint16_t rl_tail; /* The tail index (where data is removed) */ sem_t rl_exclsem; /* Enforces mutually exclusive access */ #ifndef CONFIG_RAMLOG_NONBLOCKING sem_t rl_waitsem; /* Used to wait for data */ #endif size_t rl_bufsize; /* Size of the RAM buffer */ FAR char *rl_buffer; /* Circular RAM buffer */ /* The following is a list if poll structures of threads waiting for * driver events. The 'struct pollfd' reference for each open is also * retained in the f_priv field of the 'struct file'. */ FAR struct pollfd *rl_fds[CONFIG_RAMLOG_NPOLLWAITERS]; }; /**************************************************************************** * Private Function Prototypes ****************************************************************************/ /* Helper functions */ #ifndef CONFIG_RAMLOG_NONBLOCKING static int ramlog_readnotify(FAR struct ramlog_dev_s *priv); #endif static void ramlog_pollnotify(FAR struct ramlog_dev_s *priv, pollevent_t eventset); static ssize_t ramlog_addchar(FAR struct ramlog_dev_s *priv, char ch); /* Character driver methods */ static ssize_t ramlog_read(FAR struct file *filep, FAR char *buffer, size_t buflen); static ssize_t ramlog_write(FAR struct file *filep, FAR const char *buffer, size_t buflen); static int ramlog_poll(FAR struct file *filep, FAR struct pollfd *fds, bool setup); /**************************************************************************** * Private Data ****************************************************************************/ static const struct file_operations g_ramlogfops = { NULL, /* open */ NULL, /* close */ ramlog_read, /* read */ ramlog_write, /* write */ NULL, /* seek */ NULL, /* ioctl */ ramlog_poll /* poll */ #ifndef CONFIG_DISABLE_PSEUDOFS_OPERATIONS , NULL /* unlink */ #endif }; /* This is the pre-allocated buffer used for the console RAM log and/or * for the syslogging function. */ #ifdef CONFIG_RAMLOG_SYSLOG static char g_sysbuffer[CONFIG_RAMLOG_BUFSIZE]; /* This is the device structure for the console or syslogging function. It * must be statically initialized because the RAMLOG ramlog_putc function * could be called before the driver initialization logic executes. */ static struct ramlog_dev_s g_sysdev = { #ifndef CONFIG_RAMLOG_NONBLOCKING 0, /* rl_nwaiters */ #endif 0, /* rl_head */ 0, /* rl_tail */ SEM_INITIALIZER(1), /* rl_exclsem */ #ifndef CONFIG_RAMLOG_NONBLOCKING SEM_INITIALIZER(0), /* rl_waitsem */ #endif CONFIG_RAMLOG_BUFSIZE, /* rl_bufsize */ g_sysbuffer /* rl_buffer */ }; #endif /**************************************************************************** * Private Functions ****************************************************************************/ /**************************************************************************** * Name: ramlog_readnotify ****************************************************************************/ #ifndef CONFIG_RAMLOG_NONBLOCKING static int ramlog_readnotify(FAR struct ramlog_dev_s *priv) { irqstate_t flags; int i; /* Notify all waiting readers that they can read from the FIFO */ flags = enter_critical_section(); for (i = 0; i < priv->rl_nwaiters; i++) { nxsem_post(&priv->rl_waitsem); } leave_critical_section(flags); /* Return number of notified readers. */ return i; } #endif /**************************************************************************** * Name: ramlog_pollnotify ****************************************************************************/ static void ramlog_pollnotify(FAR struct ramlog_dev_s *priv, pollevent_t eventset) { FAR struct pollfd *fds; irqstate_t flags; int i; /* This function may be called from an interrupt handler */ for (i = 0; i < CONFIG_RAMLOG_NPOLLWAITERS; i++) { flags = enter_critical_section(); fds = priv->rl_fds[i]; if (fds) { fds->revents |= (fds->events & eventset); if (fds->revents != 0) { nxsem_post(fds->sem); } } leave_critical_section(flags); } } /**************************************************************************** * Name: ramlog_addchar ****************************************************************************/ static ssize_t ramlog_addchar(FAR struct ramlog_dev_s *priv, char ch) { irqstate_t flags; size_t nexthead; /* Disable interrupts (in case we are NOT called from interrupt handler) */ flags = enter_critical_section(); /* Calculate the write index AFTER the next byte is written */ nexthead = priv->rl_head + 1; if (nexthead >= priv->rl_bufsize) { nexthead = 0; } /* Would the next write overflow the circular buffer? */ if (nexthead == priv->rl_tail) { /* Yes... Return an indication that nothing was saved in the buffer. */ leave_critical_section(flags); return -EBUSY; } /* No... copy the byte and re-enable interrupts */ priv->rl_buffer[priv->rl_head] = ch; priv->rl_head = nexthead; leave_critical_section(flags); return OK; } /**************************************************************************** * Name: ramlog_read ****************************************************************************/ static ssize_t ramlog_read(FAR struct file *filep, FAR char *buffer, size_t len) { FAR struct inode *inode = filep->f_inode; FAR struct ramlog_dev_s *priv; ssize_t nread; char ch; int ret; /* Some sanity checking */ DEBUGASSERT(inode && inode->i_private); priv = (FAR struct ramlog_dev_s *)inode->i_private; /* If the circular buffer is empty, then wait for something to be written * to it. This function may NOT be called from an interrupt handler. */ DEBUGASSERT(!up_interrupt_context()); /* Get exclusive access to the rl_tail index */ ret = nxsem_wait(&priv->rl_exclsem); if (ret < 0) { return ret; } /* Loop until something is read */ for (nread = 0; (size_t)nread < len; ) { /* Get the next byte from the buffer */ if (priv->rl_head == priv->rl_tail) { /* The circular buffer is empty. */ #ifdef CONFIG_RAMLOG_NONBLOCKING /* Return what we have (with zero mean the end-of-file) */ break; #else /* Did we read anything? */ if (nread > 0) { /* Yes.. break out to return what we have. */ break; } /* If the driver was opened with O_NONBLOCK option, then don't * wait. */ if (filep->f_oflags & O_NONBLOCK) { nread = -EAGAIN; break; } /* Otherwise, wait for something to be written to the circular * buffer. Increment the number of waiters so that the * ramlog_write() will note that it needs to post the semaphore * to wake us up. */ sched_lock(); priv->rl_nwaiters++; nxsem_post(&priv->rl_exclsem); /* We may now be pre-empted! But that should be okay because we * have already incremented nwaiters. Pre-emptions is disabled * but will be re-enabled while we are waiting. */ ret = nxsem_wait(&priv->rl_waitsem); /* Interrupts will be disabled when we return. So the decrementing * rl_nwaiters here is safe. */ priv->rl_nwaiters--; sched_unlock(); /* Did we successfully get the rl_waitsem? */ if (ret >= 0) { /* Yes... then retake the mutual exclusion semaphore */ ret = nxsem_wait(&priv->rl_exclsem); } /* Was the semaphore wait successful? Did we successful re-take the * mutual exclusion semaphore? */ if (ret < 0) { /* No.. One of the two nxsem_wait's failed. */ /* Return the error. We did handle the case where we read * anything already before waiting. */ nread = ret; /* Break out to return what we have. Note, we can't exactly * "break" out because whichever error occurred, we do not hold * the exclusion semaphore. */ goto errout_without_sem; } #endif /* CONFIG_RAMLOG_NONBLOCKING */ } else { /* The circular buffer is not empty, get the next byte from the * tail index. */ ch = priv->rl_buffer[priv->rl_tail]; /* Increment the tail index. */ if (++priv->rl_tail >= priv->rl_bufsize) { priv->rl_tail = 0; } /* Add the character to the user buffer. */ buffer[nread] = ch; nread++; } } /* Relinquish the mutual exclusion semaphore */ nxsem_post(&priv->rl_exclsem); /* Notify all poll/select waiters that they can write to the FIFO */ #ifndef CONFIG_RAMLOG_NONBLOCKING errout_without_sem: #endif if (nread > 0) { ramlog_pollnotify(priv, POLLOUT); } /* Return the number of characters actually read */ return nread; } /**************************************************************************** * Name: ramlog_write ****************************************************************************/ static ssize_t ramlog_write(FAR struct file *filep, FAR const char *buffer, size_t len) { FAR struct inode *inode = filep->f_inode; FAR struct ramlog_dev_s *priv; int readers_waken; ssize_t nwritten; char ch; int ret; /* Some sanity checking */ DEBUGASSERT(inode && inode->i_private); priv = (FAR struct ramlog_dev_s *)inode->i_private; /* Loop until all of the bytes have been written. This function may be * called from an interrupt handler! Semaphores cannot be used! * * The write logic only needs to modify the rl_head index. Therefore, * there is a difference in the way that rl_head and rl_tail are protected: * rl_tail is protected with a semaphore; rl_head is protected by disabling * interrupts. */ for (nwritten = 0; (size_t)nwritten < len; nwritten++) { /* Get the next character to output */ ch = buffer[nwritten]; /* Ignore carriage returns */ #ifdef CONFIG_RAMLOG_CRLF if (ch == '\r') { continue; } /* Pre-pend a carriage before a linefeed */ if (ch == '\n') { ret = ramlog_addchar(priv, '\r'); if (ret < 0) { /* The buffer is full and nothing was saved. The remaining * data to be written is dropped on the floor. */ break; } } #endif /* Then output the character */ ret = ramlog_addchar(priv, ch); if (ret < 0) { /* The buffer is full and nothing was saved. The remaining * data to be written is dropped on the floor. */ break; } } /* Was anything written? */ if (nwritten > 0) { readers_waken = 0; #ifndef CONFIG_RAMLOG_NONBLOCKING /* Are there threads waiting for read data? */ readers_waken = ramlog_readnotify(priv); #endif /* If there are multiple readers, some of them might block despite * POLLIN because first reader might read all data. Favor readers * and notify poll waiters only if no reader was awaken, even if the * latter may starve. * * This also implies we do not have to make these two notify * operations a critical section. */ if (readers_waken == 0) { /* Notify all poll/select waiters that they can read from the * FIFO. */ ramlog_pollnotify(priv, POLLIN); } } /* We always have to return the number of bytes requested and NOT the * number of bytes that were actually written. Otherwise, callers * probably retry, causing same error condition again. */ return len; } /**************************************************************************** * Name: ramlog_poll ****************************************************************************/ int ramlog_poll(FAR struct file *filep, FAR struct pollfd *fds, bool setup) { FAR struct inode *inode = filep->f_inode; FAR struct ramlog_dev_s *priv; pollevent_t eventset; irqstate_t flags; size_t next_head; int ret; int i; /* Some sanity checking */ DEBUGASSERT(inode && inode->i_private); priv = (FAR struct ramlog_dev_s *)inode->i_private; /* Get exclusive access to the poll structures */ ret = nxsem_wait(&priv->rl_exclsem); if (ret < 0) { return ret; } /* Are we setting up the poll? Or tearing it down? */ if (setup) { /* This is a request to set up the poll. Find an available * slot for the poll structure reference. */ for (i = 0; i < CONFIG_RAMLOG_NPOLLWAITERS; i++) { /* Find an available slot */ if (!priv->rl_fds[i]) { /* Bind the poll structure and this slot */ priv->rl_fds[i] = fds; fds->priv = &priv->rl_fds[i]; break; } } if (i >= CONFIG_RAMLOG_NPOLLWAITERS) { fds->priv = NULL; ret = -EBUSY; goto errout; } /* Should immediately notify on any of the requested events? */ eventset = 0; flags = enter_critical_section(); next_head = priv->rl_head + 1; if (next_head >= priv->rl_bufsize) { next_head = 0; } /* First, check if the receive buffer is not full. */ if (next_head != priv->rl_tail) { eventset |= POLLOUT; } /* Check if the receive buffer is not empty. */ if (priv->rl_head != priv->rl_tail) { eventset |= POLLIN; } leave_critical_section(flags); if (eventset) { ramlog_pollnotify(priv, eventset); } } else if (fds->priv) { /* This is a request to tear down the poll. */ struct pollfd **slot = (struct pollfd **)fds->priv; #ifdef CONFIG_DEBUG_FEATURES if (!slot) { ret = -EIO; goto errout; } #endif /* Remove all memory of the poll setup */ *slot = NULL; fds->priv = NULL; } errout: nxsem_post(&priv->rl_exclsem); return ret; } /**************************************************************************** * Public Functions ****************************************************************************/ /**************************************************************************** * Name: ramlog_register * * Description: * Create the RAM logging device and register it at the specified path. * ****************************************************************************/ int ramlog_register(FAR const char *devpath, FAR char *buffer, size_t buflen) { FAR struct ramlog_dev_s *priv; int ret = -ENOMEM; /* Sanity checking */ DEBUGASSERT(devpath && buffer && buflen > 1); /* Allocate a RAM logging device structure */ priv = (struct ramlog_dev_s *)kmm_zalloc(sizeof(struct ramlog_dev_s)); if (priv != NULL) { /* Initialize the non-zero values in the RAM logging device structure */ nxsem_init(&priv->rl_exclsem, 0, 1); #ifndef CONFIG_RAMLOG_NONBLOCKING nxsem_init(&priv->rl_waitsem, 0, 0); /* The rl_waitsem semaphore is used for signaling and, hence, should * not have priority inheritance enabled. */ nxsem_set_protocol(&priv->rl_waitsem, SEM_PRIO_NONE); #endif priv->rl_bufsize = buflen; priv->rl_buffer = buffer; /* Register the character driver */ ret = register_driver(devpath, &g_ramlogfops, 0666, priv); if (ret < 0) { kmm_free(priv); } } return ret; } /**************************************************************************** * Name: ramlog_syslog_register * * Description: * Use a pre-allocated RAM logging device and register it at the path * specified by CONFIG_RAMLOG_SYSLOG * ****************************************************************************/ #ifdef CONFIG_RAMLOG_SYSLOG void ramlog_syslog_register(void) { /* Register the syslog character driver */ register_driver(CONFIG_SYSLOG_DEVPATH, &g_ramlogfops, 0666, &g_sysdev); } #endif /**************************************************************************** * Name: ramlog_putc * * Description: * This is the low-level system logging interface. * ****************************************************************************/ #ifdef CONFIG_RAMLOG_SYSLOG int ramlog_putc(int ch) { FAR struct ramlog_dev_s *priv = &g_sysdev; int readers_waken = 0; int ret; #ifdef CONFIG_RAMLOG_CRLF /* Ignore carriage returns. But return success. */ if (ch == '\r') { return ch; } /* Pre-pend a newline with a carriage return */ if (ch == '\n') { ret = ramlog_addchar(priv, '\r'); if (ret < 0) { /* The buffer is full and nothing was saved. */ return ret; } } #endif /* Add the character to the RAMLOG */ ret = ramlog_addchar(priv, ch); if (ret < 0) { /* The buffer is full and 'ch' was not saved. */ return ret; } #ifndef CONFIG_RAMLOG_NONBLOCKING /* Are there threads waiting for read data? */ readers_waken = ramlog_readnotify(priv); #endif /* If there are multiple readers, some of them might block despite * POLLIN because first reader might read all data. Favor readers * and notify poll waiters only if no reader was awaken, even if the * latter may starve. * * This also implies we do not have to make these two notify * operations a critical section. */ if (readers_waken == 0) { /* Notify all poll/select waiters that they can read from the FIFO */ ramlog_pollnotify(priv, POLLIN); } /* Return the character added on success */ return ch; } #endif #endif /* CONFIG_RAMLOG */