linux-kernel - Re: [PATCH] hid-mcp2200: added driver for GPIOs of MCP2200

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Date:   Fri, 28 Jul 2023 00:30:53 +0200
From:   Christophe JAILLET <christophe.jaillet@...adoo.fr>
To:     Johannes Roith <johannes@...-linux.rocks>, jikos@...nel.org,
        benjamin.tissoires@...hat.com
Cc:     linux-kernel@...r.kernel.org, linux-input@...r.kernel.org,
        andi.shyti@...nel.org
Subject: Re: [PATCH] hid-mcp2200: added driver for GPIOs of MCP2200

Le 23/06/2023 à 13:01, Johannes Roith a écrit :
> Added a gpiochip compatible driver to control the 8 GPIOs of the MCP2200
> by using the HID interface.
> 
> Using GPIOs with alternative functions (GP0<->SSPND, GP1<->USBCFG,
> GP6<->RXLED, GP7<->TXLED) will reset the functions, if set (unset by
> default).
> 
> The driver was tested while also using the UART of the chip. Setting
> and reading the GPIOs has no effect on the UART communication. However,
> a reset is triggered after the CONFIGURE command. If the GPIO Direction
> is constantly changed, this will affect the communication at low baud
> rates. This is a hardware problem of the MCP2200 and is not caused by
> the driver.
> 
> Feedback from reviewers Christophe JAILLET <christophe.jaillet@...adoo.fr>
> and Andi Shyti <andi.shyti@...nel.org> was added.
> 
> Signed-off-by: Johannes Roith <johannes@...-linux.rocks>
> ---

[...]

> +static int mcp2200_probe(struct hid_device *hdev, const struct hid_device_id *id)
> +{
> +	int ret;
> +	struct mcp2200 *mcp;
> +
> +	mcp = devm_kzalloc(&hdev->dev, sizeof(*mcp), GFP_KERNEL);
> +	if (!mcp)
> +		return -ENOMEM;
> +
> +	ret = hid_parse(hdev);
> +	if (ret) {
> +		hid_err(hdev, "can't parse reports\n");
> +		return ret;
> +	}
> +
> +	/*
> +	 * This driver uses the .raw_event callback and therefore does not need any
> +	 * HID_CONNECT_xxx flags.
> +	 */
> +	ret = hid_hw_start(hdev, 0);
> +	if (ret) {
> +		hid_err(hdev, "can't start hardware\n");
> +		return ret;
> +	}
> +
> +	hid_info(hdev, "USB HID v%x.%02x Device [%s] on %s\n", hdev->version >> 8,
> +			hdev->version & 0xff, hdev->name, hdev->phys);
> +
> +	ret = hid_hw_open(hdev);
> +	if (ret) {
> +		hid_err(hdev, "can't open device\n");
> +		hid_hw_stop(hdev);
> +		return ret;
> +	}
> +
> +	mutex_init(&mcp->lock);
> +	init_completion(&mcp->wait_in_report);
> +	hid_set_drvdata(hdev, mcp);
> +	mcp->hdev = hdev;
> +
> +	ret = devm_add_action_or_reset(&hdev->dev, mcp2200_hid_unregister, hdev);
> +	if (ret)
> +		return ret;
> +
> +	mcp->gc = template_chip;
> +	mcp->gc.parent = &hdev->dev;
> +
> +	ret = gpiochip_add_data(&mcp->gc, mcp);

devm_gpiochip_add_data()?

> +	if (ret < 0) {
> +		dev_err(&hdev->dev, "Unable to register gpiochip\n");

hid_err() to be consistent?

> +		hid_hw_stop(hdev);

Isn't it already run by mcp2200_hid_unregister() registered a few lines 
above?

CJ

> +		return ret;
> +	}
> +
> +	return 0;
> +}
> +
> +static void mcp2200_remove(struct hid_device *hdev)
> +{
> +	struct mcp2200 *mcp;
> +
> +	mcp = hid_get_drvdata(hdev);
> +	gpiochip_remove(&mcp->gc);
> +}
> +

[...]