/**
* flush_write_buffer - push buffer to kobject
* @of: open file
* @buf: data buffer for file
* @off: file offset to write to
* @count: number of bytes
*
* Get the correct pointers for the kobject and the attribute we're dealing
* with, then call the store() method for it with @buf.
*/
static int flush_write_buffer(struct sysfs_open_file *of, char *buf, loff_t off,
size_t count)
{
struct kobject *kobj = of->sd->s_parent->s_dir.kobj;
int rc = 0;
/*
* Need @of->sd for attr and ops, its parent for kobj. @of->mutex
* nests outside active ref and is just to ensure that the ops
* aren't called concurrently for the same open file.
*/
mutex_lock(&of->mutex);
if (!sysfs_get_active(of->sd)) {
mutex_unlock(&of->mutex);
return -ENODEV;
}
if (sysfs_is_bin(of->sd)) {
struct bin_attribute *battr = of->sd->s_attr.bin_attr;
rc = -EIO;
if (battr->write)
rc = battr->write(of->file, kobj, battr, buf, off,
count);
} else {
const struct sysfs_ops *ops = sysfs_file_ops(of->sd);
rc = ops->store(kobj, of->sd->s_attr.attr, buf, count);
}
sysfs_put_active(of->sd);
mutex_unlock(&of->mutex);
return rc;
}
/**
* sysfs_write_file - write an attribute
* @file: file pointer
* @user_buf: data to write
* @count: number of bytes
* @ppos: starting offset
*
* Copy data in from userland and pass it to the matching
* sysfs_ops->store() by invoking flush_write_buffer().
*
* There is no easy way for us to know if userspace is only doing a partial
* write, so we don't support them. We expect the entire buffer to come on
* the first write. Hint: if you're writing a value, first read the file,
* modify only the the value you're changing, then write entire buffer
* back.
*/
static ssize_t sysfs_write_file(struct file *file, const char __user *user_buf,
size_t count, loff_t *ppos)
{
struct sysfs_open_file *of = sysfs_of(file);
ssize_t len = min_t(size_t, count, PAGE_SIZE);
loff_t size = file_inode(file)->i_size;
char *buf;
if (sysfs_is_bin(of->sd) && size) {
if (size <= *ppos)
return 0;
len = min_t(ssize_t, len, size - *ppos);
}
if (!len)
return 0;
buf = kmalloc(len + 1, GFP_KERNEL);
if (!buf)
return -ENOMEM;
if (copy_from_user(buf, user_buf, len)) {
len = -EFAULT;
goto out_free;
}
buf[len] = '\0'; /* guarantee string termination */
len = flush_write_buffer(of, buf, *ppos, len);
if (len > 0)
*ppos += len;
out_free:
kfree(buf);
return len;
}