static void keyspan_check_data()

in misc/keyspan_remote.c [179:329]

• 122 lines of code
• 23 McCabe index (conditional complexity)

static void keyspan_check_data(struct usb_keyspan *remote)
{
	int i;
	int found = 0;
	struct keyspan_message message;

	switch(remote->stage) {
	case 0:
		/*
		 * In stage 0 we want to find the start of a message.  The remote sends a 0xFF as filler.
		 * So the first byte that isn't a FF should be the start of a new message.
		 */
		for (i = 0; i < RECV_SIZE && remote->in_buffer[i] == GAP; ++i);

		if (i < RECV_SIZE) {
			memcpy(remote->data.buffer, remote->in_buffer, RECV_SIZE);
			remote->data.len = RECV_SIZE;
			remote->data.pos = 0;
			remote->data.tester = 0;
			remote->data.bits_left = 0;
			remote->stage = 1;
		}
		break;

	case 1:
		/*
		 * Stage 1 we should have 16 bytes and should be able to detect a
		 * SYNC.  The SYNC is 14 bits, 7 0's and then 7 1's.
		 */
		memcpy(remote->data.buffer + remote->data.len, remote->in_buffer, RECV_SIZE);
		remote->data.len += RECV_SIZE;

		found = 0;
		while ((remote->data.bits_left >= 14 || remote->data.pos < remote->data.len) && !found) {
			for (i = 0; i < 8; ++i) {
				if (keyspan_load_tester(remote, 14) != 0) {
					remote->stage = 0;
					return;
				}

				if ((remote->data.tester & SYNC_MASK) == SYNC) {
					remote->data.tester = remote->data.tester >> 14;
					remote->data.bits_left -= 14;
					found = 1;
					break;
				} else {
					remote->data.tester = remote->data.tester >> 1;
					--remote->data.bits_left;
				}
			}
		}

		if (!found) {
			remote->stage = 0;
			remote->data.len = 0;
		} else {
			remote->stage = 2;
		}
		break;

	case 2:
		/*
		 * Stage 2 we should have 24 bytes which will be enough for a full
		 * message.  We need to parse out the system code, button code,
		 * toggle code, and stop.
		 */
		memcpy(remote->data.buffer + remote->data.len, remote->in_buffer, RECV_SIZE);
		remote->data.len += RECV_SIZE;

		message.system = 0;
		for (i = 0; i < 9; i++) {
			keyspan_load_tester(remote, 6);

			if ((remote->data.tester & ZERO_MASK) == ZERO) {
				message.system = message.system << 1;
				remote->data.tester = remote->data.tester >> 5;
				remote->data.bits_left -= 5;
			} else if ((remote->data.tester & ONE_MASK) == ONE) {
				message.system = (message.system << 1) + 1;
				remote->data.tester = remote->data.tester >> 6;
				remote->data.bits_left -= 6;
			} else {
				dev_err(&remote->interface->dev,
					"%s - Unknown sequence found in system data.\n",
					__func__);
				remote->stage = 0;
				return;
			}
		}

		message.button = 0;
		for (i = 0; i < 5; i++) {
			keyspan_load_tester(remote, 6);

			if ((remote->data.tester & ZERO_MASK) == ZERO) {
				message.button = message.button << 1;
				remote->data.tester = remote->data.tester >> 5;
				remote->data.bits_left -= 5;
			} else if ((remote->data.tester & ONE_MASK) == ONE) {
				message.button = (message.button << 1) + 1;
				remote->data.tester = remote->data.tester >> 6;
				remote->data.bits_left -= 6;
			} else {
				dev_err(&remote->interface->dev,
					"%s - Unknown sequence found in button data.\n",
					__func__);
				remote->stage = 0;
				return;
			}
		}

		keyspan_load_tester(remote, 6);
		if ((remote->data.tester & ZERO_MASK) == ZERO) {
			message.toggle = 0;
			remote->data.tester = remote->data.tester >> 5;
			remote->data.bits_left -= 5;
		} else if ((remote->data.tester & ONE_MASK) == ONE) {
			message.toggle = 1;
			remote->data.tester = remote->data.tester >> 6;
			remote->data.bits_left -= 6;
		} else {
			dev_err(&remote->interface->dev,
				"%s - Error in message, invalid toggle.\n",
				__func__);
			remote->stage = 0;
			return;
		}

		keyspan_load_tester(remote, 5);
		if ((remote->data.tester & STOP_MASK) == STOP) {
			remote->data.tester = remote->data.tester >> 5;
			remote->data.bits_left -= 5;
		} else {
			dev_err(&remote->interface->dev,
				"Bad message received, no stop bit found.\n");
		}

		dev_dbg(&remote->interface->dev,
			"%s found valid message: system: %d, button: %d, toggle: %d\n",
			__func__, message.system, message.button, message.toggle);

		if (message.toggle != remote->toggle) {
			keyspan_report_button(remote, message.button, 1);
			keyspan_report_button(remote, message.button, 0);
			remote->toggle = message.toggle;
		}

		remote->stage = 0;
		break;
	}
}