Re: [PATCH] input: tegra: Use of_property_read_variable_u32_array() and of_property_present()

[Dmitry Torokhov <dmitry.torokhov@gmail.com>]

On Tue, Aug 27, 2024 at 04:23:48PM +0200, Thierry Reding wrote:
> 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@nvidia.com>

I don't quite like of_property_read_variable_u32_array() because it is
OF-specific. device_property_count_u32() will return the number of
elements in an array. But I guess this driver will only be used on an OF
system... 

Applied, thank you.

-- 
Dmitry