linux-kernel - Re: [PATCH] Input: zinitix - Don't fail if linux,keycodes prop is absent

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Message-ID: <Zv6Dai0WOSn8GOsr@google.com>
Date: Thu, 3 Oct 2024 04:43:38 -0700
From: Dmitry Torokhov <dmitry.torokhov@...il.com>
To: Nikita Travkin <nikita@...n.ru>
Cc: Linus Walleij <linus.walleij@...aro.org>, linux-input@...r.kernel.org,
	linux-kernel@...r.kernel.org, Jakob Hauser <jahau@...ketmail.com>
Subject: Re: [PATCH] Input: zinitix - Don't fail if linux,keycodes prop is
 absent

Hi Nikita,

On Wed, Oct 02, 2024 at 06:01:48PM +0500, Nikita Travkin wrote:
> When initially adding the touchkey support, a mistake was made in the
> property parsing code. The possible negative errno from
> device_property_count_u32() was never checked, which was an oversight
> left from converting to it from the of_property as part of the review
> fixes.
> 
> Re-add the correct handling of the absent property, in which case zero
> touchkeys should be assumed, which would disable the feature.
> 
> Reported-by: Jakob Hauser <jahau@...ketmail.com>
> Tested-by: Jakob Hauser <jahau@...ketmail.com>
> Fixes: 075d9b22c8fe ("Input: zinitix - add touchkey support")
> Signed-off-by: Nikita Travkin <nikita@...n.ru>
> ---
>  drivers/input/touchscreen/zinitix.c | 33 ++++++++++++++++++++++-----------
>  1 file changed, 22 insertions(+), 11 deletions(-)
> 
> diff --git a/drivers/input/touchscreen/zinitix.c b/drivers/input/touchscreen/zinitix.c
> index 52b3950460e2..1f726653940c 100644
> --- a/drivers/input/touchscreen/zinitix.c
> +++ b/drivers/input/touchscreen/zinitix.c
> @@ -645,19 +645,30 @@ static int zinitix_ts_probe(struct i2c_client *client)
>  		return error;
>  	}
>  
> -	bt541->num_keycodes = device_property_count_u32(&client->dev, "linux,keycodes");
> -	if (bt541->num_keycodes > ARRAY_SIZE(bt541->keycodes)) {
> -		dev_err(&client->dev, "too many keys defined (%d)\n", bt541->num_keycodes);
> -		return -EINVAL;
> +	error = device_property_count_u32(&client->dev, "linux,keycodes");
> +	if (error == -EINVAL || error == -ENODATA) {
> +		bt541->num_keycodes = 0;
> +	} else if (error < 0) {
> +		dev_err(&client->dev, "Failed to count \"linux,keycodes\" property: %d\n", error);
> +		return error;
> +	} else {
> +		bt541->num_keycodes = error;
>  	}
>  
> -	error = device_property_read_u32_array(&client->dev, "linux,keycodes",
> -					       bt541->keycodes,
> -					       bt541->num_keycodes);
> -	if (error) {
> -		dev_err(&client->dev,
> -			"Unable to parse \"linux,keycodes\" property: %d\n", error);
> -		return error;
> +	if (bt541->num_keycodes > 0) {

I think this check is not needed and "if" can be folded into "else"
above. But anyways, do you mind if I rewrite it as follows:

	...

	n_keycodes = device_property_count_u32(&client->dev, "linux,keycodes");
	if (n_keycodes < 0) {
		error = n_keycodes;
		if (error != -EINVAL && error != -ENODATA) {
			dev_err(&client->dev,
				"Failed to count \"linux,keycodes\" property: %d\n",
				error);
			return error;
		}
	} else if (n_keycodes > 0) {
		if (n_keycodes > ARRAY_SIZE(bt541->keycodes)) {
			dev_err(&client->dev,
				"too many keys defined (%d)\n", n_keycodes);
			return -EINVAL;
		}

		error = device_property_read_u32_array(&client->dev,
						       "linux,keycodes",
						       bt541->keycodes,
						       n_keycodes);
		if (error) {
			dev_err(&client->dev,
				"Unable to parse \"linux,keycodes\" property: %d\n",
				error);
			return error;
		}

		bt541->num_keycodes = n_keycodes;
	}


Or maybe to avoid checking for specific error codes we should do:

	if (device_property_present(&client->dev, "linux,keycodes")) {
		bt541->num_keycodes = device_property_count_u32(&client->dev,
								"linux,keycodes");
		if (bt541->num_keycodes < 0) {
			error = bt541->num_keycodes;
			dev_err(&client->dev, ...);
			return error;
		}

		...
	}


Thanks.

-- 
Dmitry