linux-kernel - Re: [PATCH] input: tegra: Use of_property_read_variable_u32_array() and of_property

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Message-ID: <zyzygwdfncus7nhnu6sgbc2wzjpih3dntgdogorg3it4vc7r6v@aufrf6kwqun3>
Date: Tue, 27 Aug 2024 16:23:48 +0200
From: Thierry Reding <thierry.reding@...il.com>
To: "Rob Herring (Arm)" <robh@...nel.org>
Cc: Laxman Dewangan <ldewangan@...dia.com>, 
	Dmitry Torokhov <dmitry.torokhov@...il.com>, Jonathan Hunter <jonathanh@...dia.com>, 
	linux-input@...r.kernel.org, linux-tegra@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] input: tegra: Use of_property_read_variable_u32_array()
 and of_property_present()

On Wed, Jul 31, 2024 at 02:14:01PM GMT, Rob Herring (Arm) wrote:
> There's no need to get the length of an DT array property before
> parsing the array. of_property_read_variable_u32_array() takes a
> minimum and maximum length and returns the actual length (or error
> code).
> 
> This is part of a larger effort to remove callers of of_get_property()
> and similar functions. of_get_property() leaks the DT property data
> pointer which is a problem for dynamically allocated nodes which may
> be freed.
> ---
>  drivers/input/keyboard/tegra-kbc.c | 72 +++++++++++-------------------
>  1 file changed, 27 insertions(+), 45 deletions(-)
> 
> diff --git a/drivers/input/keyboard/tegra-kbc.c b/drivers/input/keyboard/tegra-kbc.c
> index a1765ed8c825..53f39fc155ea 100644
> --- a/drivers/input/keyboard/tegra-kbc.c
> +++ b/drivers/input/keyboard/tegra-kbc.c
> @@ -491,12 +491,10 @@ static int tegra_kbc_parse_dt(struct tegra_kbc *kbc)
>  	struct device_node *np = kbc->dev->of_node;
>  	u32 prop;
>  	int i;
> -	u32 num_rows = 0;
> -	u32 num_cols = 0;
> +	int num_rows;
> +	int num_cols;
>  	u32 cols_cfg[KBC_MAX_GPIO];
>  	u32 rows_cfg[KBC_MAX_GPIO];
> -	int proplen;
> -	int ret;
>  
>  	if (!of_property_read_u32(np, "nvidia,debounce-delay-ms", &prop))
>  		kbc->debounce_cnt = prop;
> @@ -510,56 +508,23 @@ static int tegra_kbc_parse_dt(struct tegra_kbc *kbc)
>  	    of_property_read_bool(np, "nvidia,wakeup-source")) /* legacy */
>  		kbc->wakeup = true;
>  
> -	if (!of_get_property(np, "nvidia,kbc-row-pins", &proplen)) {
> -		dev_err(kbc->dev, "property nvidia,kbc-row-pins not found\n");
> -		return -ENOENT;
> -	}
> -	num_rows = proplen / sizeof(u32);
> -
> -	if (!of_get_property(np, "nvidia,kbc-col-pins", &proplen)) {
> -		dev_err(kbc->dev, "property nvidia,kbc-col-pins not found\n");
> -		return -ENOENT;
> -	}
> -	num_cols = proplen / sizeof(u32);
> -
> -	if (num_rows > kbc->hw_support->max_rows) {
> -		dev_err(kbc->dev,
> -			"Number of rows is more than supported by hardware\n");
> -		return -EINVAL;
> -	}
> -
> -	if (num_cols > kbc->hw_support->max_columns) {
> -		dev_err(kbc->dev,
> -			"Number of cols is more than supported by hardware\n");
> -		return -EINVAL;
> -	}
> -
> -	if (!of_get_property(np, "linux,keymap", &proplen)) {
> +	if (!of_property_present(np, "linux,keymap")) {
>  		dev_err(kbc->dev, "property linux,keymap not found\n");
>  		return -ENOENT;
>  	}
>  
> -	if (!num_rows || !num_cols || ((num_rows + num_cols) > KBC_MAX_GPIO)) {
> -		dev_err(kbc->dev,
> -			"keypad rows/columns not properly specified\n");
> -		return -EINVAL;
> -	}
> -
>  	/* Set all pins as non-configured */
>  	for (i = 0; i < kbc->num_rows_and_columns; i++)
>  		kbc->pin_cfg[i].type = PIN_CFG_IGNORE;
>  
> -	ret = of_property_read_u32_array(np, "nvidia,kbc-row-pins",
> -				rows_cfg, num_rows);
> -	if (ret < 0) {
> +	num_rows = of_property_read_variable_u32_array(np, "nvidia,kbc-row-pins",
> +				rows_cfg, 1, KBC_MAX_GPIO);
> +	if (num_rows < 0) {
>  		dev_err(kbc->dev, "Rows configurations are not proper\n");
> -		return -EINVAL;
> -	}
> -
> -	ret = of_property_read_u32_array(np, "nvidia,kbc-col-pins",
> -				cols_cfg, num_cols);
> -	if (ret < 0) {
> -		dev_err(kbc->dev, "Cols configurations are not proper\n");
> +		return num_rows;
> +	} else if (num_rows > kbc->hw_support->max_rows) {
> +		dev_err(kbc->dev,
> +			"Number of rows is more than supported by hardware\n");
>  		return -EINVAL;
>  	}
>  
> @@ -568,11 +533,28 @@ static int tegra_kbc_parse_dt(struct tegra_kbc *kbc)
>  		kbc->pin_cfg[rows_cfg[i]].num = i;
>  	}
>  
> +	num_cols = of_property_read_variable_u32_array(np, "nvidia,kbc-col-pins",
> +				cols_cfg, 1, KBC_MAX_GPIO);
> +	if (num_cols < 0) {
> +		dev_err(kbc->dev, "Cols configurations are not proper\n");
> +		return num_cols;
> +	} else if (num_cols > kbc->hw_support->max_columns) {
> +		dev_err(kbc->dev,
> +			"Number of cols is more than supported by hardware\n");
> +		return -EINVAL;
> +	}
> +
>  	for (i = 0; i < num_cols; i++) {
>  		kbc->pin_cfg[cols_cfg[i]].type = PIN_CFG_COL;
>  		kbc->pin_cfg[cols_cfg[i]].num = i;
>  	}
>  
> +	if (!num_rows || !num_cols || ((num_rows + num_cols) > KBC_MAX_GPIO)) {
> +		dev_err(kbc->dev,
> +			"keypad rows/columns not properly specified\n");
> +		return -EINVAL;
> +	}

Previously we wouldn't try to initialize the columns when the
rows/columns were invalid, so this block could move before the last for
loop above.

But it doesn't really matter given that these are exceptions and really
shouldn't happen, so:

Acked-by: Thierry Reding <treding@...dia.com>

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