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

Tomasz Duszynski
2019-01-08T19:08:25Z

On Mon, Jan 07, 2019 at 04:35:42PM +0100, Johan Hovold wrote:
> 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.
>

Right, on the second though that can be simplified by just ignoring
return value I guess. Anyway, thanks for pointing this out.

> Johan