linux-kernel - Re: [PATCH v2 1/3] HID: mcp2221: don't connect hidraw

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Date:   Mon, 19 Dec 2022 15:11:10 +0100
From:   Benjamin Tissoires <benjamin.tissoires@...hat.com>
To:     Enrik Berkhan <Enrik.Berkhan@...a.de>
Cc:     linux-input@...r.kernel.org, linux-i2c@...r.kernel.org,
        Sven Zühlsdorf <sven.zuehlsdorf@...em.de>,
        linux-kernel@...r.kernel.org, Rishi Gupta <gupt21@...il.com>
Subject: Re: [PATCH v2 1/3] HID: mcp2221: don't connect hidraw

On Nov 03 2022, Enrik Berkhan wrote:
> The MCP2221 driver should not connect to the hidraw userspace interface,
> as it needs exclusive access to the chip.
> 
> If you want to use /dev/hidrawX with the MCP2221, you need to avoid
> binding this driver to the device and use the hid generic driver instead
> (e.g. using udev rules).
> 
> Signed-off-by: Enrik Berkhan <Enrik.Berkhan@...a.de>
> ---

Given the NULL pointer deference report at
https://lore.kernel.org/all/79152feb-bcbc-9e3e-e776-13170ae4ef40@vigem.de/

I have added:
Reported-by: Sven Zühlsdorf <sven.zuehlsdorf@...em.de>
And applied this one only in the series in for-6.2/upstream-fixes.

Before applying the rest I'd rather have some external reviews of this
series.

Cheers,
Benjamin

>  drivers/hid/hid-mcp2221.c | 12 +++++++++---
>  1 file changed, 9 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/hid/hid-mcp2221.c b/drivers/hid/hid-mcp2221.c
> index 5886543b17f3..e61dd039354b 100644
> --- a/drivers/hid/hid-mcp2221.c
> +++ b/drivers/hid/hid-mcp2221.c
> @@ -1110,12 +1110,19 @@ static int mcp2221_probe(struct hid_device *hdev,
>  		return ret;
>  	}
>  
> -	ret = hid_hw_start(hdev, HID_CONNECT_HIDRAW);
> +	/*
> +	 * 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");
> @@ -1145,8 +1152,7 @@ static int mcp2221_probe(struct hid_device *hdev,
>  	mcp->adapter.retries = 1;
>  	mcp->adapter.dev.parent = &hdev->dev;
>  	snprintf(mcp->adapter.name, sizeof(mcp->adapter.name),
> -			"MCP2221 usb-i2c bridge on hidraw%d",
> -			((struct hidraw *)hdev->hidraw)->minor);
> +			"MCP2221 usb-i2c bridge");
>  
>  	ret = devm_i2c_add_adapter(&hdev->dev, &mcp->adapter);
>  	if (ret) {
> -- 
> 2.34.1
>