On 12/12/2013 12:57 AM, Hiroshi Doyu wrote:

The device, which belongs to the same ASID, can try to enable the same
ASID as the other swgroup devices. This should be allowed but just
skip the actual register write. If the write value is different, it
will return -EINVAL.

I guess this simplifies the body of the code a lot. Given this, I would
revise the code I suggested in response to a previous patch, to
something more like:

		offs = HWGRP_ASID_REG(i);
		val = smmu_read(smmu, offs);
		if (on) {
			if (WARN_ON(val && val != new_val))
				return -ENODEV;
			memcpy(c->hwgrp, map, sizeof(u64));
		} else {
			WARN_ON(val);
		}
		smmu_write(smmu, val, offs);

+			if (val) {
+				if (WARN_ON(val != mask))
+					return -EINVAL;
+				goto skip;

That means that:

a) No error is returned when the ASIDs don't match. Surely you still
want to return an error?

b) "skip" skips setting up all HWGRP IDs for the device, whereas perhaps
only 1 was shared yet the rest still need to be set up. If you really do
want to ignore the error, then surely you want "continue;" here not
"goto skip;"?

+			}

...

+skip:
 	return 0;