Re: [RFC 2/2] input: evdev: Add EVIOC mechanism to extract the MT slot state

On Thu, Jan 27, 2011 at 01:09:45PM +0100, Henrik Rydberg wrote:

On Thu, Jan 27, 2011 at 11:35:47AM +0100, Benjamin Tissoires wrote:

quoted

This patch adds the ability to extract the MT slot state sequentially
via EVIOCGABS. The slot parameter is first selected by calling
EVIOCSABS with ABS_MT_SLOT as argument, followed by a set of EVIOCGABS
calls. The slot selection is local to the evdev client handler, and
does not affect the actual input state.

Ok - it seemed like a reasonable idea at the time, but..

quoted

@@ -767,9 +769,10 @@ static long evdev_do_ioctl(struct file *file, unsigned int cmd,
 			if (size < sizeof(struct input_absinfo))
 				abs.resolution = 0;
 
-			/* We can't change number of reserved MT slots */
-			if (t == ABS_MT_SLOT)
-				return -EINVAL;
+			if (t == ABS_MT_SLOT) {
+				client->slot = abs.value;
+				return 0;
+			}

...this just does not look right. Perhaps there should really be a
different ioctl to retrieve the slot values instead. Dmitry?

Yes, a separate ioctl with explicit slot number is much better option.
Then it is automatically multi-thread safe and just does not look
ugly as hell.

Thanks.

-- 
Dmitry