void w1_search()

in w1.c [989:1095]

• 72 lines of code
• 19 McCabe index (conditional complexity)

void w1_search(struct w1_master *dev, u8 search_type, w1_slave_found_callback cb)
{
	u64 last_rn, rn, tmp64;
	int i, slave_count = 0;
	int last_zero, last_device;
	int search_bit, desc_bit;
	u8  triplet_ret = 0;

	search_bit = 0;
	rn = dev->search_id;
	last_rn = 0;
	last_device = 0;
	last_zero = -1;

	desc_bit = 64;

	while ( !last_device && (slave_count++ < dev->max_slave_count) ) {
		last_rn = rn;
		rn = 0;

		/*
		 * Reset bus and all 1-wire device state machines
		 * so they can respond to our requests.
		 *
		 * Return 0 - device(s) present, 1 - no devices present.
		 */
		mutex_lock(&dev->bus_mutex);
		if (w1_reset_bus(dev)) {
			mutex_unlock(&dev->bus_mutex);
			dev_dbg(&dev->dev, "No devices present on the wire.\n");
			break;
		}

		/* Do fast search on single slave bus */
		if (dev->max_slave_count == 1) {
			int rv;
			w1_write_8(dev, W1_READ_ROM);
			rv = w1_read_block(dev, (u8 *)&rn, 8);
			mutex_unlock(&dev->bus_mutex);

			if (rv == 8 && rn)
				cb(dev, rn);

			break;
		}

		/* Start the search */
		w1_write_8(dev, search_type);
		for (i = 0; i < 64; ++i) {
			/* Determine the direction/search bit */
			if (i == desc_bit)
				search_bit = 1;	  /* took the 0 path last time, so take the 1 path */
			else if (i > desc_bit)
				search_bit = 0;	  /* take the 0 path on the next branch */
			else
				search_bit = ((last_rn >> i) & 0x1);

			/* Read two bits and write one bit */
			triplet_ret = w1_triplet(dev, search_bit);

			/* quit if no device responded */
			if ( (triplet_ret & 0x03) == 0x03 )
				break;

			/* If both directions were valid, and we took the 0 path... */
			if (triplet_ret == 0)
				last_zero = i;

			/* extract the direction taken & update the device number */
			tmp64 = (triplet_ret >> 2);
			rn |= (tmp64 << i);

			if (test_bit(W1_ABORT_SEARCH, &dev->flags)) {
				mutex_unlock(&dev->bus_mutex);
				dev_dbg(&dev->dev, "Abort w1_search\n");
				return;
			}
		}
		mutex_unlock(&dev->bus_mutex);

		if ( (triplet_ret & 0x03) != 0x03 ) {
			if ((desc_bit == last_zero) || (last_zero < 0)) {
				last_device = 1;
				dev->search_id = 0;
			} else {
				dev->search_id = rn;
			}
			desc_bit = last_zero;
			cb(dev, rn);
		}

		if (!last_device && slave_count == dev->max_slave_count &&
			!test_bit(W1_WARN_MAX_COUNT, &dev->flags)) {
			/* Only max_slave_count will be scanned in a search,
			 * but it will start where it left off next search
			 * until all ids are identified and then it will start
			 * over.  A continued search will report the previous
			 * last id as the first id (provided it is still on the
			 * bus).
			 */
			dev_info(&dev->dev, "%s: max_slave_count %d reached, "
				"will continue next search.\n", __func__,
				dev->max_slave_count);
			set_bit(W1_WARN_MAX_COUNT, &dev->flags);
		}
	}
}