ssize_t scullc_write (struct file *filp, const char __user *buf, size_t count, loff_t *f_pos) { struct scullc_dev *dev = filp->private_data; struct scullc_dev *dptr; int quantum = dev->quantum; int qset = dev->qset; int itemsize = quantum * qset; int item, s_pos, q_pos, rest; ssize_t retval = -ENOMEM; /* our most likely error */ if (down_interruptible (&dev->sem)) return -ERESTARTSYS; /* find listitem, qset index and offset in the quantum */ item = ((long) *f_pos) / itemsize; rest = ((long) *f_pos) % itemsize; s_pos = rest / quantum; q_pos = rest % quantum; /* follow the list up to the right position */ dptr = scullc_follow(dev, item); if (!dptr->data) { dptr->data = kmalloc(qset * sizeof(void *), GFP_KERNEL); if (!dptr->data) goto nomem; memset(dptr->data, 0, qset * sizeof(char *)); } /* Allocate a quantum using the memory cache */ if (!dptr->data[s_pos]) { dptr->data[s_pos] = kmem_cache_alloc(scullc_cache, GFP_KERNEL); if (!dptr->data[s_pos]) goto nomem; memset(dptr->data[s_pos], 0, scullc_quantum); } if (count > quantum - q_pos) count = quantum - q_pos; /* write only up to the end of this quantum */ if (copy_from_user (dptr->data[s_pos]+q_pos, buf, count)) { retval = -EFAULT; goto nomem; } *f_pos += count; /* update the size */ if (dev->size < *f_pos) dev->size = *f_pos; up (&dev->sem); return count; nomem: up (&dev->sem); return retval; }
ssize_t scullc_read (struct file *filp, char __user *buf, size_t count, loff_t *f_pos) { struct scullc_dev *dev = filp->private_data; /* the first listitem */ struct scullc_dev *dptr; int quantum = dev->quantum; int qset = dev->qset; int itemsize = quantum * qset; /* how many bytes in the listitem */ int item, s_pos, q_pos, rest; ssize_t retval = 0; if (down_interruptible (&dev->sem)) return -ERESTARTSYS; if (*f_pos > dev->size) goto nothing; if (*f_pos + count > dev->size) count = dev->size - *f_pos; /* find listitem, qset index, and offset in the quantum */ item = ((long) *f_pos) / itemsize; rest = ((long) *f_pos) % itemsize; s_pos = rest / quantum; q_pos = rest % quantum; /* follow the list up to the right position (defined elsewhere) */ dptr = scullc_follow(dev, item); if (!dptr->data) goto nothing; /* don't fill holes */ if (!dptr->data[s_pos]) goto nothing; if (count > quantum - q_pos) count = quantum - q_pos; /* read only up to the end of this quantum */ if (copy_to_user (buf, dptr->data[s_pos]+q_pos, count)) { retval = -EFAULT; goto nothing; } up (&dev->sem); *f_pos += count; return count; nothing: up (&dev->sem); return retval; }