Hello.
The funtion "clk_find(dev_id, con_id)" takes the most specific entry - with the following order of precedence: dev_id+con_id > dev_id only > con_id only,but actually it doesn't work very well. 
In the code,
"		if (p->dev_id) {
			if (!dev_id || strcmp(p->dev_id, dev_id))
				continue;
			match += 2;
		}
		if (p->con_id) {
			if (!con_id || strcmp(p->con_id, con_id))
				continue;
			match += 1;
		}
		if (match > best_found) {
			cl = p;
			if (match != best_possible)
				best_found = match;
			else
				break;
		}
"
it uses the "continue", then we can assume that if only dev_id matches,and con_id doesn't match,it enters into next loop,so c1 is equal to NULL.After the lists has been traversed,the c1 is still equal to NULL.But in fact we can find a clock that matches the dev_id.This function only works well when dev_id and con_id are all matched at the same time.
I suggest that we could modify like this for example:
"		if (p->dev_id) {
			if (!dev_id || strcmp(p->dev_id, dev_id))
				match = match;
                        else
			        match += 2;
		}
		if (p->con_id) {
			if (!con_id || strcmp(p->con_id, con_id))
				match = match;
                        else
			        match += 1;
		}
 "
Thanks for your reading!