static int read_one_response()

in fsi-master-gpio.c [334:395]

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

static int read_one_response(struct fsi_master_gpio *master,
		uint8_t data_size, struct fsi_gpio_msg *msgp, uint8_t *tagp)
{
	struct fsi_gpio_msg msg;
	unsigned long flags;
	uint32_t crc;
	uint8_t tag;
	int i;

	local_irq_save(flags);

	/* wait for the start bit */
	for (i = 0; i < FSI_MASTER_MTOE_COUNT; i++) {
		msg.bits = 0;
		msg.msg = 0;
		serial_in(master, &msg, 1);
		if (msg.msg)
			break;
	}
	if (i == FSI_MASTER_MTOE_COUNT) {
		dev_dbg(master->dev,
			"Master time out waiting for response\n");
		local_irq_restore(flags);
		return -ETIMEDOUT;
	}

	msg.bits = 0;
	msg.msg = 0;

	/* Read slave ID & response tag */
	serial_in(master, &msg, 4);

	tag = msg.msg & 0x3;

	/* If we have an ACK and we're expecting data, clock the data in too */
	if (tag == FSI_RESP_ACK && data_size)
		serial_in(master, &msg, data_size * 8);

	/* read CRC */
	serial_in(master, &msg, FSI_CRC_SIZE);

	local_irq_restore(flags);

	/* we have a whole message now; check CRC */
	crc = crc4(0, 1, 1);
	crc = crc4(crc, msg.msg, msg.bits);
	if (crc) {
		/* Check if it's all 1's, that probably means the host is off */
		if (((~msg.msg) & ((1ull << msg.bits) - 1)) == 0)
			return -ENODEV;
		dev_dbg(master->dev, "ERR response CRC msg: 0x%016llx (%d bits)\n",
			msg.msg, msg.bits);
		return -EAGAIN;
	}

	if (msgp)
		*msgp = msg;
	if (tagp)
		*tagp = tag;

	return 0;
}