Re: [PATCH 1/3] iio: chemical: add support for Plantower PMS7003 sensor

Johan Hovold
2019-01-07T15:35:46Z

On Sun, Jan 06, 2019 at 06:16:12PM +0100, Tomasz Duszynski wrote:
> Add support for Plantower PMS7003 particulate matter sensor.
>
> Signed-off-by: Tomasz Duszynski <tduszyns@gmail.com>

> +static int pms7003_do_cmd(struct pms7003_state *state, u8 cmd)
> +{
> + /*
> + * commands have following format:
> + *
> + * +------+------+-----+------+-----+-----------+-----------+
> + * | 0x42 | 0x4d | cmd | 0x00 | arg | cksum msb | cksum lsb |
> + * +------+------+-----+------+-----+-----------+-----------+
> + */
> + u8 tmp[PMS7003_CMD_LENGTH] = { PMS7003_MAGIC_MSB, PMS7003_MAGIC_LSB };
> + int ret, n = 2;
> + u16 checksum;
> +
> + switch (cmd) {
> + case CMD_WAKEUP:
> + tmp[n++] = 0xe4;
> + tmp[n++] = 0x00;
> + tmp[n++] = 0x01;
> + break;
> + case CMD_ENTER_PASSIVE_MODE:
> + tmp[n++] = 0xe1;
> + tmp[n++] = 0x00;
> + tmp[n++] = 0x00;
> + break;
> + case CMD_READ_PASSIVE:
> + tmp[n++] = 0xe2;
> + tmp[n++] = 0x00;
> + tmp[n++] = 0x00;
> + break;
> + case CMD_SLEEP:
> + tmp[n++] = 0xe4;
> + tmp[n++] = 0x00;
> + tmp[n++] = 0x00;
> + break;
> + }
> +
> + checksum = pms7003_calc_checksum(tmp, n);
> + put_unaligned_be16(checksum, tmp + n);
> + n += PMS7003_CHECKSUM_LENGTH;
> +
> + ret = serdev_device_write(state->serdev, tmp, n, PMS7003_TIMEOUT);
> + if (ret)
> + return ret;

Beginning with 5.0, serdev_device_write() returns the number of bytes
written before timeout (or being interrupted) so you need to check
against < n here.

Johan