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sparc: Add support for seek and shorter read to /dev/mdesc 

/dev/mdesc on Linux does not support reading arbitrary number
of bytes and seeking while /dev/mdesc on Solaris does. This
causes tools that work on Solaris to break on Linux. This patch
adds these two capabilities to /dev/mdesc.

Signed-off-by: Khalid Aziz <khalid.aziz@oracle.com>
Acked-by: Sam Ravnborg <sam@ravnborg.org>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Khalid Aziz 2014-07-18 09:15:40 -06:00 committed by David S. Miller
parent e7fbaf016e
commit 07d6692133
1 changed files with 69 additions and 13 deletions
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82
arch/sparc/kernel/mdesc.c
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@ -906,29 +906,85 @@ void mdesc_fill_in_cpu_data(cpumask_t *mask)
smp_fill_in_sib_core_maps();
}
static ssize_t mdesc_read(struct file *file, char __user *buf,
size_t len, loff_t *offp)
/* mdesc_open() - Grab a reference to mdesc_handle when /dev/mdesc is
* opened. Hold this reference until /dev/mdesc is closed to ensure
* mdesc data structure is not released underneath us. Store the
* pointer to mdesc structure in private_data for read and seek to use
*/
static int mdesc_open(struct inode *inode, struct file *file)
{
struct mdesc_handle *hp = mdesc_grab();
int err;
if (!hp)
return -ENODEV;
err = hp->handle_size;
if (len < hp->handle_size)
err = -EMSGSIZE;
else if (copy_to_user(buf, &hp->mdesc, hp->handle_size))
err = -EFAULT;
mdesc_release(hp);
file->private_data = hp;
return err;
return 0;
}
static ssize_t mdesc_read(struct file *file, char __user *buf,
size_t len, loff_t *offp)
{
struct mdesc_handle *hp = file->private_data;
unsigned char *mdesc;
int bytes_left, count = len;
if (*offp >= hp->handle_size)
return 0;
bytes_left = hp->handle_size - *offp;
if (count > bytes_left)
count = bytes_left;
mdesc = (unsigned char *)&hp->mdesc;
mdesc += *offp;
if (!copy_to_user(buf, mdesc, count)) {
*offp += count;
return count;
} else {
return -EFAULT;
}
}
static loff_t mdesc_llseek(struct file *file, loff_t offset, int whence)
{
struct mdesc_handle *hp;
switch (whence) {
case SEEK_CUR:
offset += file->f_pos;
break;
case SEEK_SET:
break;
default:
return -EINVAL;
}
hp = file->private_data;
if (offset > hp->handle_size)
return -EINVAL;
else
file->f_pos = offset;
return offset;
}
/* mdesc_close() - /dev/mdesc is being closed, release the reference to
* mdesc structure.
*/
static int mdesc_close(struct inode *inode, struct file *file)
{
mdesc_release(file->private_data);
return 0;
}
static const struct file_operations mdesc_fops = {
.read = mdesc_read,
.owner = THIS_MODULE,
.llseek = noop_llseek,
.open = mdesc_open,
.read = mdesc_read,
.llseek = mdesc_llseek,
.release = mdesc_close,
.owner = THIS_MODULE,
};
static struct miscdevice mdesc_misc = {