ieee1394: cycle timer read extension for raw1394

This implements the simultaneous read of the isochronous cycle timer and
the system clock (in usecs).  This allows to express the exact receive
time of an ISO packet as a system time with microsecond accuracy.
http://bugzilla.kernel.org/show_bug.cgi?id=7773

The counterpart patch for libraw1394 can be found at
http://thread.gmane.org/gmane.linux.kernel.firewire.devel/8934

Patch update (Stefan R.):  Disable preemption and local interrupts.
Prevent integer overflow.  Add paranoid error checks and kerneldoc to
hpsb_read_cycle_timer.  Move it to other ieee1394_core high-level API
functions.  Change comments.  Adjust whitespace.  Rename struct
_raw1394_cycle_timer.

Signed-off-by: Stefan Richter <stefanr@s5r6.in-berlin.de>
Acked-by: Pieter Palmers <pieterp@joow.be>
Acked-by: Dan Dennedy <dan@dennedy.org>

1 files changed, 20 insertions, 0 deletions

diff --git a/drivers/ieee1394/raw1394.c b/drivers/ieee1394/raw1394.c
index a77a832..5d08d74 100644
--- a/drivers/ieee1394/raw1394.c
+++ b/drivers/ieee1394/raw1394.c
@@ -2669,6 +2669,18 @@ static void raw1394_iso_shutdown(struct file_info *fi)
 	fi->iso_state = RAW1394_ISO_INACTIVE;
 }
 
+static int raw1394_read_cycle_timer(struct file_info *fi, void __user * uaddr)
+{
+	struct raw1394_cycle_timer ct;
+	int err;
+
+	err = hpsb_read_cycle_timer(fi->host, &ct.cycle_timer, &ct.local_time);
+	if (!err)
+		if (copy_to_user(uaddr, &ct, sizeof(ct)))
+			err = -EFAULT;
+	return err;
+}
+
 /* mmap the rawiso xmit/recv buffer */
 static int raw1394_mmap(struct file *file, struct vm_area_struct *vma)
 {
@@ -2777,6 +2789,14 @@ static int raw1394_ioctl(struct inode *inode, struct file *file,
 		break;
 	}
 
+	/* state-independent commands */
+	switch(cmd) {
+	case RAW1394_IOC_GET_CYCLE_TIMER:
+		return raw1394_read_cycle_timer(fi, argp);
+	default:
+		break;
+	}
+
 	return -EINVAL;
 }