static int ds1302_probe()

in rtc-ds1302.c [104:186]

• 69 lines of code
• 14 McCabe index (conditional complexity)

static int ds1302_probe(struct spi_device *spi)
{
	struct rtc_device	*rtc;
	u8		addr;
	u8		buf[4];
	u8		*bp;
	int		status;

	/* Sanity check board setup data.  This may be hooked up
	 * in 3wire mode, but we don't care.  Note that unless
	 * there's an inverter in place, this needs SPI_CS_HIGH!
	 */
	if (spi->bits_per_word && (spi->bits_per_word != 8)) {
		dev_err(&spi->dev, "bad word length\n");
		return -EINVAL;
	} else if (spi->max_speed_hz > 2000000) {
		dev_err(&spi->dev, "speed is too high\n");
		return -EINVAL;
	} else if (spi->mode & SPI_CPHA) {
		dev_err(&spi->dev, "bad mode\n");
		return -EINVAL;
	}

	addr = RTC_ADDR_CTRL << 1 | RTC_CMD_READ;
	status = spi_write_then_read(spi, &addr, sizeof(addr), buf, 1);
	if (status < 0) {
		dev_err(&spi->dev, "control register read error %d\n",
				status);
		return status;
	}

	if ((buf[0] & ~RTC_CMD_WRITE_DISABLE) != 0) {
		status = spi_write_then_read(spi, &addr, sizeof(addr), buf, 1);
		if (status < 0) {
			dev_err(&spi->dev, "control register read error %d\n",
					status);
			return status;
		}

		if ((buf[0] & ~RTC_CMD_WRITE_DISABLE) != 0) {
			dev_err(&spi->dev, "junk in control register\n");
			return -ENODEV;
		}
	}
	if (buf[0] == 0) {
		bp = buf;
		*bp++ = RTC_ADDR_CTRL << 1 | RTC_CMD_WRITE;
		*bp++ = RTC_CMD_WRITE_DISABLE;

		status = spi_write_then_read(spi, buf, 2, NULL, 0);
		if (status < 0) {
			dev_err(&spi->dev, "control register write error %d\n",
					status);
			return status;
		}

		addr = RTC_ADDR_CTRL << 1 | RTC_CMD_READ;
		status = spi_write_then_read(spi, &addr, sizeof(addr), buf, 1);
		if (status < 0) {
			dev_err(&spi->dev,
					"error %d reading control register\n",
					status);
			return status;
		}

		if (buf[0] != RTC_CMD_WRITE_DISABLE) {
			dev_err(&spi->dev, "failed to detect chip\n");
			return -ENODEV;
		}
	}

	spi_set_drvdata(spi, spi);

	rtc = devm_rtc_device_register(&spi->dev, "ds1302",
			&ds1302_rtc_ops, THIS_MODULE);
	if (IS_ERR(rtc)) {
		status = PTR_ERR(rtc);
		dev_err(&spi->dev, "error %d registering rtc\n", status);
		return status;
	}

	return 0;
}