linux-kernel - Re: [PATCH v5 1/1] platform/chrome: add a driver for HPS

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Date:   Wed, 12 Oct 2022 16:46:51 +0800
From:   Tzung-Bi Shih <tzungbi@...nel.org>
To:     Dan Callaghan <dcallagh@...omium.org>
Cc:     chrome-platform@...ts.linux.dev,
        LKML <linux-kernel@...r.kernel.org>,
        Sami Kyöstilä <skyostil@...omium.org>,
        Benson Leung <bleung@...omium.org>
Subject: Re: [PATCH v5 1/1] platform/chrome: add a driver for HPS

On Wed, Oct 12, 2022 at 03:09:18PM +1100, Dan Callaghan wrote:
> ---

It doesn't need a cover letter if the series only has 1 patch in general.
Instead, it could put additional information (and changelogs) after "---".

> diff --git a/drivers/platform/chrome/cros_hps_i2c.c b/drivers/platform/chrome/cros_hps_i2c.c
[...]
> +static int hps_i2c_probe(struct i2c_client *client)
> +{
> +	struct hps_drvdata *hps;
> +	int ret;
> +
> +	hps = devm_kzalloc(&client->dev, sizeof(*hps), GFP_KERNEL);
> +	if (!hps)
> +		return -ENOMEM;
> +
> +	memset(&hps->misc_device, 0, sizeof(hps->misc_device));

The memset can be dropped.  `hps` is z-allocated.

> +	hps->misc_device.parent = &client->dev;
> +	hps->misc_device.minor = MISC_DYNAMIC_MINOR;
> +	hps->misc_device.name = "cros-hps";
> +	hps->misc_device.fops = &hps_fops;
> +
> +	i2c_set_clientdata(client, hps);
> +	hps->client = client;

To be neat, I would prefer to insert a blank line here.

> +	hps->enable_gpio = devm_gpiod_get(&client->dev, "enable", GPIOD_OUT_HIGH);
> +	if (IS_ERR(hps->enable_gpio)) {
> +		ret = PTR_ERR(hps->enable_gpio);
> +		dev_err(&client->dev, "failed to get enable gpio: %d\n", ret);
> +		return ret;
> +	}
> +
> +	ret = misc_register(&hps->misc_device);
> +	if (ret) {
> +		dev_err(&client->dev, "failed to initialize misc device: %d\n", ret);
> +		return ret;
> +	}
> +
> +	hps_set_power(hps, false);

IIUC, the GPIO will raise to HIGH in the first place, and then fall
to LOW until here.  Is it an expected behavior?  How about gpiod_get()
with GPIOD_OUT_LOW?

> +static int hps_i2c_remove(struct i2c_client *client)
> +{
> +	struct hps_drvdata *hps = i2c_get_clientdata(client);
> +
> +	pm_runtime_disable(&client->dev);
> +	misc_deregister(&hps->misc_device);
> +	hps_set_power(hps, true);

Why does it need to raise the GPIO again when removing the device?