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Commit 07d66921 authored by Khalid Aziz's avatar Khalid Aziz Committed by David S. Miller
Browse files

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: default avatarKhalid Aziz <khalid.aziz@oracle.com>
Acked-by: default avatarSam Ravnborg <sam@ravnborg.org>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent e7fbaf01

arch/sparc/kernel/mdesc.c

+69 −13
Original line number Original line Diff line number Diff line
@@ -906,29 +906,85 @@ void mdesc_fill_in_cpu_data(cpumask_t *mask) 
	smp_fill_in_sib_core_maps();

	smp_fill_in_sib_core_maps();

}

}





static ssize_t mdesc_read(struct file *file, char __user *buf,

/* mdesc_open() - Grab a reference to mdesc_handle when /dev/mdesc is

			  size_t len, loff_t *offp)

 * 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();

	struct mdesc_handle *hp = mdesc_grab();

	int err;





	if (!hp)

	if (!hp)

		return -ENODEV;

		return -ENODEV;





	err = hp->handle_size;

	file->private_data = hp;

	if (len < hp->handle_size)



		err = -EMSGSIZE;

	return 0;

	else if (copy_to_user(buf, &hp->mdesc, hp->handle_size))

}

		err = -EFAULT;



	mdesc_release(hp);

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;

	}

}





	return err;

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 = {

static const struct file_operations mdesc_fops = {

	.open    = mdesc_open,

	.read	 = mdesc_read,

	.read	 = mdesc_read,

	.llseek  = mdesc_llseek,

	.release = mdesc_close,

	.owner	 = THIS_MODULE,

	.owner	 = THIS_MODULE,

	.llseek = noop_llseek,

};

};





static struct miscdevice mdesc_misc = {

static struct miscdevice mdesc_misc = {