linux-kernel - Re: [PATCH v3 2/4] iio: chemical: scd30: add I2C interface driver

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Message-ID: <CAHp75Vc60q1PC9j6KR1-OJHxw=nBAHt9zJK=h9f27yJxMHpb8A@mail.gmail.com>
Date:   Tue, 2 Jun 2020 20:14:13 +0300
From:   Andy Shevchenko <andy.shevchenko@...il.com>
To:     Tomasz Duszynski <tomasz.duszynski@...akon.com>
Cc:     linux-iio <linux-iio@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        devicetree <devicetree@...r.kernel.org>,
        Rob Herring <robh+dt@...nel.org>,
        Jonathan Cameron <jic23@...nel.org>,
        Peter Meerwald <pmeerw@...erw.net>
Subject: Re: [PATCH v3 2/4] iio: chemical: scd30: add I2C interface driver

On Tue, Jun 2, 2020 at 7:49 PM Tomasz Duszynski
<tomasz.duszynski@...akon.com> wrote:
>
> Add I2C interface driver for the SCD30 sensor.

...

> +static u16 scd30_i2c_cmd_lookup_tbl[] = {
> +       [CMD_START_MEAS] = 0x0010,
> +       [CMD_STOP_MEAS] = 0x0104,
> +       [CMD_MEAS_INTERVAL] = 0x4600,
> +       [CMD_MEAS_READY] = 0x0202,
> +       [CMD_READ_MEAS] = 0x0300,
> +       [CMD_ASC] = 0x5306,
> +       [CMD_FRC] = 0x5204,
> +       [CMD_TEMP_OFFSET] = 0x5403,
> +       [CMD_FW_VERSION] = 0xd100,
> +       [CMD_RESET] = 0xd304,

Keep sorted by value?

> +};

...

> +       ret = i2c_master_send(client, txbuf, txsize);

> +       if (ret != txsize)
> +               return ret < 0 ? ret : -EIO;

Wouldn't be better

  if (ret < 0)
    return ret;
  if (ret != txsize)
    return -EIO;

?

> +       if (!rxbuf)
> +               return 0;
> +
> +       ret = i2c_master_recv(client, rxbuf, rxsize);

> +       if (ret != rxsize)
> +               return ret < 0 ? ret : -EIO;

Ditto.

...

> +static int scd30_i2c_command(struct scd30_state *state, enum scd30_cmd cmd,
> +                            u16 arg, void *response, int size)
> +{
> +       char crc, buf[SCD30_I2C_MAX_BUF_SIZE], *rsp = response;
> +       int i, ret;

i -> offset ?

> +       put_unaligned_be16(scd30_i2c_cmd_lookup_tbl[cmd], buf);
> +       i = 2;
> +
> +       if (rsp) {
> +               /* each two bytes are followed by a crc8 */
> +               size += size / 2;
> +       } else {
> +               put_unaligned_be16(arg, buf + i);
> +               crc = crc8(scd30_i2c_crc8_tbl, buf + i, 2, CRC8_INIT_VALUE);
> +               i += 2;

> +               buf[i] = crc;
> +               i += 1;

buf[offset++] = crc; ?

> +               /* commands below don't take an argument */
> +               if ((cmd == CMD_STOP_MEAS) || (cmd == CMD_RESET))
> +                       i -= 3;
> +       }
> +
> +       ret = scd30_i2c_xfer(state, buf, i, buf, size);
> +       if (ret)
> +               return ret;
> +
> +       /* validate received data and strip off crc bytes */
> +       for (i = 0; i < size; i += 3) {
> +               crc = crc8(scd30_i2c_crc8_tbl, buf + i, 2, CRC8_INIT_VALUE);
> +               if (crc != buf[i + 2]) {
> +                       dev_err(state->dev, "data integrity check failed\n");
> +                       return -EIO;
> +               }
> +

> +               *rsp++ = buf[i];

+ 0 (for the sake of consistency?

> +               *rsp++ = buf[i + 1];
> +       }
> +
> +       return 0;
> +}

...

> +static struct i2c_driver scd30_i2c_driver = {
> +       .driver = {

> +               .name = KBUILD_MODNAME,

Better to hard code.

> +               .of_match_table = scd30_i2c_of_match,
> +               .pm = &scd30_pm_ops,
> +       },
> +       .probe_new = scd30_i2c_probe,
> +};

-- 
With Best Regards,
Andy Shevchenko