linux kernel write()
ssize_t read(struct file *filp, char *buff,
size_t count, loff_t *offp);
ssize_t write(struct file *filp, const char *buff,
size_t count, loff_t *offp);linux kernel write()
ssize_t read(struct file *filp, char *buff,
size_t count, loff_t *offp);
ssize_t write(struct file *filp, const char *buff,
size_t count, loff_t *offp);linux kernel write()
ssize_t scull_write(struct file *filp, const char *buf, size_t count,
loff_t *f_pos)
{
Scull_Dev *dev = filp->private_data;
Scull_Dev *dptr;
int quantum = dev->quantum;
int qset = dev->qset;
int itemsize = quantum * qset;
int item, s_pos, q_pos, rest;
ssize_t ret = -ENOMEM; /* value used in "goto out" statements */
if (down_interruptible(&dev->sem))
return -ERESTARTSYS;
/* find list item, 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 = scull_follow(dev, item);
if (!dptr->data) {
dptr->data = kmalloc(qset * sizeof(char *), GFP_KERNEL);
if (!dptr->data)
goto out;
memset(dptr->data, 0, qset * sizeof(char *));
}
if (!dptr->data[s_pos]) {
dptr->data[s_pos] = kmalloc(quantum, GFP_KERNEL);
if (!dptr->data[s_pos])
goto out;
}
/* write only up to the end of this quantum */
if (count > quantum - q_pos)
count = quantum - q_pos;
if (copy_from_user(dptr->data[s_pos]+q_pos, buf, count)) {
ret = -EFAULT;
goto out;
}
*f_pos += count;
ret = count;
/* update the size */
if (dev->size < *f_pos)
dev-> size = *f_pos;
out:
up(&dev->sem);
return ret;
}linux kernel write()
unsigned long copy_to_user(void *to, const void *from,
unsigned long count);
unsigned long copy_from_user(void *to, const void *from,
unsigned long count);linux kernel write()
ssize_t (*readv) (struct file *filp, const struct iovec *iov,
unsigned long count, loff_t *ppos);
ssize_t (*writev) (struct file *filp, const struct iovec *iov,
unsigned long count, loff_t *ppos);linux kernel write()
ssize_t scull_read(struct file *filp, char *buf, size_t count,
loff_t *f_pos)
{
Scull_Dev *dev = filp->private_data; /* the first list item */
Scull_Dev *dptr;
int quantum = dev->quantum;
int qset = dev->qset;
int itemsize = quantum * qset; /* how many bytes in the list item */
int item, s_pos, q_pos, rest;
ssize_t ret = 0;
if (down_interruptible(&dev->sem))
return -ERESTARTSYS;
if (*f_pos >= dev->size)
goto out;
if (*f_pos + count > dev->size)
count = dev->size - *f_pos;
/* find list item, 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 = scull_follow(dev, item);
if (!dptr->data)
goto out; /* don't fill holes */
if (!dptr->data[s_pos])
goto out;
/* read only up to the end of this quantum */
if (count > quantum - q_pos)
count = quantum - q_pos;
if (copy_to_user(buf, dptr->data[s_pos]+q_pos, count)) {
ret = -EFAULT;
goto out;
}
*f_pos += count;
ret = count;
out:
up(&dev->sem);
return ret;
}Copyright © 2021 Codeinu
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