static void ds1wm_search()

in masters/ds1wm.c [371:495]

• 99 lines of code
• 10 McCabe index (conditional complexity)

static void ds1wm_search(void *data, struct w1_master *master_dev,
			u8 search_type, w1_slave_found_callback slave_found)
{
	struct ds1wm_data *ds1wm_data = data;
	int i;
	int ms_discrep_bit = -1;
	u64 r = 0; /* holds the progress of the search */
	u64 r_prime, d;
	unsigned slaves_found = 0;
	unsigned int pass = 0;

	dev_dbg(&ds1wm_data->pdev->dev, "search begin\n");
	while (true) {
		++pass;
		if (pass > 100) {
			dev_dbg(&ds1wm_data->pdev->dev,
				"too many attempts (100), search aborted\n");
			return;
		}

		mutex_lock(&master_dev->bus_mutex);
		if (ds1wm_reset(ds1wm_data)) {
			mutex_unlock(&master_dev->bus_mutex);
			dev_dbg(&ds1wm_data->pdev->dev,
				"pass: %d reset error (or no slaves)\n", pass);
			break;
		}

		dev_dbg(&ds1wm_data->pdev->dev,
			"pass: %d r : %0#18llx writing SEARCH_ROM\n", pass, r);
		ds1wm_write(ds1wm_data, search_type);
		dev_dbg(&ds1wm_data->pdev->dev,
			"pass: %d entering ASM\n", pass);
		ds1wm_write_register(ds1wm_data, DS1WM_CMD, DS1WM_CMD_SRA);
		dev_dbg(&ds1wm_data->pdev->dev,
			"pass: %d beginning nibble loop\n", pass);

		r_prime = 0;
		d = 0;
		/* we work one nibble at a time */
		/* each nibble is interleaved to form a byte */
		for (i = 0; i < 16; i++) {

			unsigned char resp, _r, _r_prime, _d;

			_r = (r >> (4*i)) & 0xf;
			_r = ((_r & 0x1) << 1) |
			((_r & 0x2) << 2) |
			((_r & 0x4) << 3) |
			((_r & 0x8) << 4);

			/* writes _r, then reads back: */
			resp = ds1wm_read(ds1wm_data, _r);

			if (ds1wm_data->read_error) {
				dev_err(&ds1wm_data->pdev->dev,
				"pass: %d nibble: %d read error\n", pass, i);
				break;
			}

			_r_prime = ((resp & 0x02) >> 1) |
			((resp & 0x08) >> 2) |
			((resp & 0x20) >> 3) |
			((resp & 0x80) >> 4);

			_d = ((resp & 0x01) >> 0) |
			((resp & 0x04) >> 1) |
			((resp & 0x10) >> 2) |
			((resp & 0x40) >> 3);

			r_prime |= (unsigned long long) _r_prime << (i * 4);
			d |= (unsigned long long) _d << (i * 4);

		}
		if (ds1wm_data->read_error) {
			mutex_unlock(&master_dev->bus_mutex);
			dev_err(&ds1wm_data->pdev->dev,
				"pass: %d read error, retrying\n", pass);
			break;
		}
		dev_dbg(&ds1wm_data->pdev->dev,
			"pass: %d r\': %0#18llx d:%0#18llx\n",
			pass, r_prime, d);
		dev_dbg(&ds1wm_data->pdev->dev,
			"pass: %d nibble loop complete, exiting ASM\n", pass);
		ds1wm_write_register(ds1wm_data, DS1WM_CMD, ~DS1WM_CMD_SRA);
		dev_dbg(&ds1wm_data->pdev->dev,
			"pass: %d resetting bus\n", pass);
		ds1wm_reset(ds1wm_data);
		mutex_unlock(&master_dev->bus_mutex);
		if ((r_prime & ((u64)1 << 63)) && (d & ((u64)1 << 63))) {
			dev_err(&ds1wm_data->pdev->dev,
				"pass: %d bus error, retrying\n", pass);
			continue; /* start over */
		}


		dev_dbg(&ds1wm_data->pdev->dev,
			"pass: %d found %0#18llx\n", pass, r_prime);
		slave_found(master_dev, r_prime);
		++slaves_found;
		dev_dbg(&ds1wm_data->pdev->dev,
			"pass: %d complete, preparing next pass\n", pass);

		/* any discrepency found which we already choose the
		   '1' branch is now is now irrelevant we reveal the
		   next branch with this: */
		d &= ~r;
		/* find last bit set, i.e. the most signif. bit set */
		ms_discrep_bit = fls64(d) - 1;
		dev_dbg(&ds1wm_data->pdev->dev,
			"pass: %d new d:%0#18llx MS discrep bit:%d\n",
			pass, d, ms_discrep_bit);

		/* prev_ms_discrep_bit = ms_discrep_bit;
		   prepare for next ROM search:		    */
		if (ms_discrep_bit == -1)
			break;

		r = (r &  ~(~0ull << (ms_discrep_bit))) | 1 << ms_discrep_bit;
	} /* end while true */
	dev_dbg(&ds1wm_data->pdev->dev,
		"pass: %d total: %d search done ms d bit pos: %d\n", pass,
		slaves_found, ms_discrep_bit);
}