ssize_t uORB::DeviceNode::read(struct file *filp, char *buffer, size_t buflen) { SubscriberData *sd = (SubscriberData *)filp_to_sd(filp); /* if the object has not been written yet, return zero */ if (_data == nullptr) { return 0; } /* if the caller's buffer is the wrong size, that's an error */ if (buflen != _meta->o_size) { return -EIO; } /* * Perform an atomic copy & state update */ irqstate_t flags = px4_enter_critical_section(); if (_generation > sd->generation + _queue_size) { /* Reader is too far behind: some messages are lost */ _lost_messages += _generation - (sd->generation + _queue_size); sd->generation = _generation - _queue_size; } if (_generation == sd->generation && sd->generation > 0) { /* The subscriber already read the latest message, but nothing new was published yet. * Return the previous message */ --sd->generation; } /* if the caller doesn't want the data, don't give it to them */ if (nullptr != buffer) { memcpy(buffer, _data + (_meta->o_size * (sd->generation % _queue_size)), _meta->o_size); } if (sd->generation < _generation) { ++sd->generation; } /* set priority */ sd->set_priority(_priority); /* * Clear the flag that indicates that an update has been reported, as * we have just collected it. */ sd->set_update_reported(false); px4_leave_critical_section(flags); return _meta->o_size; }
int uORB::DeviceNode::open(struct file *filp) { int ret; /* is this a publisher? */ if (filp->f_oflags == O_WRONLY) { /* become the publisher if we can */ lock(); if (_publisher == 0) { _publisher = getpid(); ret = OK; } else { ret = -EBUSY; } unlock(); /* now complete the open */ if (ret == OK) { ret = CDev::open(filp); /* open failed - not the publisher anymore */ if (ret != OK) { _publisher = 0; } } return ret; } /* is this a new subscriber? */ if (filp->f_oflags == O_RDONLY) { /* allocate subscriber data */ SubscriberData *sd = new SubscriberData; if (nullptr == sd) { return -ENOMEM; } memset(sd, 0, sizeof(*sd)); /* default to no pending update */ sd->generation = _generation; /* set priority */ sd->set_priority(_priority); filp->f_priv = (void *)sd; ret = CDev::open(filp); add_internal_subscriber(); if (ret != OK) { delete sd; } return ret; } /* can only be pub or sub, not both */ return -EINVAL; }
int uORB::DeviceNode::open(cdev::file_t *filp) { int ret; /* is this a publisher? */ if (FILE_FLAGS(filp) == PX4_F_WRONLY) { /* become the publisher if we can */ lock(); if (_publisher == 0) { _publisher = px4_getpid(); ret = PX4_OK; } else { ret = -EBUSY; } unlock(); /* now complete the open */ if (ret == PX4_OK) { ret = CDev::open(filp); /* open failed - not the publisher anymore */ if (ret != PX4_OK) { _publisher = 0; } } return ret; } /* is this a new subscriber? */ if (FILE_FLAGS(filp) == PX4_F_RDONLY) { /* allocate subscriber data */ SubscriberData *sd = new SubscriberData{}; if (nullptr == sd) { return -ENOMEM; } /* If there were any previous publications, allow the subscriber to read them */ sd->generation = _generation - (_queue_size < _generation ? _queue_size : _generation); /* set priority */ sd->set_priority(_priority); FILE_PRIV(filp) = (void *)sd; ret = CDev::open(filp); add_internal_subscriber(); if (ret != PX4_OK) { PX4_ERR("CDev::open failed"); delete sd; } return ret; } if (FILE_FLAGS(filp) == 0) { return CDev::open(filp); } /* can only be pub or sub, not both */ return -EINVAL; }