linux-kernel - Re: [PATCH v7 2/2] iio: light: Add support for ltrf216a sensor

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Date:   Mon, 11 Jul 2022 19:09:15 +0530
From:   Shreeya Patel <shreeya.patel@...labora.com>
To:     Andy Shevchenko <andy.shevchenko@...il.com>
Cc:     Jonathan Cameron <jic23@...nel.org>,
        Lars-Peter Clausen <lars@...afoo.de>,
        Rob Herring <robh+dt@...nel.org>, Zhigang.Shi@...eon.com,
        krisman@...labora.com, linux-iio <linux-iio@...r.kernel.org>,
        devicetree <devicetree@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Collabora Kernel ML <kernel@...labora.com>,
        alvaro.soliverez@...labora.com, dmitry.osipenko@...labora.com
Subject: Re: [PATCH v7 2/2] iio: light: Add support for ltrf216a sensor


On 11/07/22 18:36, Andy Shevchenko wrote:
> On Mon, Jul 11, 2022 at 1:30 PM Shreeya Patel
> <shreeya.patel@...labora.com> wrote:
>> From: Zhigang Shi <Zhigang.Shi@...eon.com>
>>
>> Add initial support for ltrf216a ambient light sensor.
>>
>> Datasheet: https://gitlab.steamos.cloud/shreeya/iio/-/blob/main/LTRF216A.pdf
>> Co-developed-by: Shreeya Patel <shreeya.patel@...labora.com>
>> Signed-off-by: Shreeya Patel <shreeya.patel@...labora.com>
>> Signed-off-by: Zhigang Shi <Zhigang.Shi@...eon.com>
> Submitter's SoB always has to be last among SoBs in the proposed change.
> https://www.kernel.org/doc/html/latest/process/submitting-patches.html#sign-your-work-the-developer-s-certificate-of-origin
> https://www.kernel.org/doc/html/latest/process/submitting-patches.html#when-to-use-acked-by-cc-and-co-developed-by
>
> ...
>
>> +static int ltrf216a_set_power_state(struct ltrf216a_data *data, bool on)
>> +{
>> +       struct device *dev = &data->client->dev;
>> +       int ret;
>> +
>> +       if (on) {
>> +               ret = pm_runtime_resume_and_get(dev);
>> +               if (ret < 0) {
>> +                       dev_err(dev, "Failed to resume runtime PM: %d\n", ret);
>> +                       return ret;
>> +               }
>> +
> Unneeded blank line.
>
>> +       } else {
>> +               pm_runtime_mark_last_busy(dev);
>> +               ret = pm_runtime_put_autosuspend(dev);
>> +       }
>> +
>> +       return ret;
>> +}
> ...
>
>> +       ret = regmap_read_poll_timeout(data->regmap, LTRF216A_MAIN_STATUS,
>> +                                      val, val & LTRF216A_ALS_DATA_STATUS,
>> +                                      LTRF216A_ALS_READ_DATA_DELAY_US,
>> +                                      LTRF216A_ALS_READ_DATA_DELAY_US * 50);
>> +       if (ret) {
>> +               dev_err(dev, "Timed out waiting for valid data from LTRF216A_MAIN_STATUS reg: %d\n",
>> +                       ret);
> THe message is a bit misleading. The loop might be broken by the I/O error.
>
>> +               return ret;
>> +       }
>> +
>> +       ret = regmap_bulk_read(data->regmap, addr, buf, sizeof(buf));
>> +       if (ret < 0) {
>> +               dev_err(dev, "Error reading measurement data: %d\n", ret);
>> +               return ret;
>> +       }
> ...
>
>> +static const struct regmap_config ltrf216a_regmap_config = {
>> +       .name = LTRF216A_DRV_NAME,
>> +       .reg_bits = 8,
>> +       .val_bits = 8,
>> +       .max_register = LTRF216A_MAX_REG,
> Why do you use regmap locking? What for?
>
Hi Andy,

Why do we want to skip the internal locking if it doesn't bring any 
benefits?


>> +};
> ...
>
>> +       data->regmap = devm_regmap_init_i2c(client, &ltrf216a_regmap_config);
>> +       if (IS_ERR(data->regmap)) {
>> +               dev_err(&client->dev, "Regmap initialization failed.\n");
>> +               return PTR_ERR(data->regmap);
> return dev_err_probe(...);
>
>> +       }
> ...
>
>> +       ret = devm_pm_runtime_enable(&client->dev);
>> +       if (ret < 0) {
>> +               dev_err_probe(&client->dev, ret, "Failed to enable runtime PM\n");
>> +               return ret;
> Ditto.
>
>> +       }
> ...
>
>> +               ret = ltrf216a_init(indio_dev);
>> +               if (ret) {
>> +                       dev_err_probe(&client->dev, ret, "Failed to enable the sensor\n");
>> +                       return ret;
> Ditto.
>
>> +               }
> ...
>
>> +       if (ret < 0)
> For all these  ' < 0', please explain what positive return value means
> there, if any, and why it's being ignored.
>
> ...
>
>> +static const struct i2c_device_id ltrf216a_id[] = {
>> +       { LTRF216A_DRV_NAME, 0 },
> Please, use the string literal directly since it's kinda an ABI,
> defining above for potential changes is not a good idea. Also you may
> drop the ', 0' part.
>
>> +       {}
>> +};
> ...
>
>> +static struct i2c_driver ltrf216a_driver = {
>> +       .driver = {
>> +               .name = LTRF216A_DRV_NAME,
> Ditto.
>
>> +               .pm = pm_ptr(&ltrf216a_pm_ops),
>> +               .of_match_table = ltrf216a_of_match,
>> +       },
>> +       .probe_new      = ltrf216a_probe,
>> +       .id_table       = ltrf216a_id,
>> +};