Re: [PATCH] leds: qcom-lpg: allocate channels with main struct

[Lee Jones <lee@kernel.org>]

On Mon, 30 Mar 2026, Rosen Penev wrote:

> Use a flexible array member to combine kzalloc and kcalloc. This
> required moving the struct lpg_channel definition up as flexible array
> members require a full definition.
> 
> Add __counted_by for extra runtime analysis.
> 
> Signed-off-by: Rosen Penev <rosenp@gmail.com>
> ---
>  drivers/leds/rgb/leds-qcom-lpg.c | 117 +++++++++++++++----------------
>  1 file changed, 56 insertions(+), 61 deletions(-)
> 
> diff --git a/drivers/leds/rgb/leds-qcom-lpg.c b/drivers/leds/rgb/leds-qcom-lpg.c
> index f6061c47f863..83cedf4a0cbf 100644
> --- a/drivers/leds/rgb/leds-qcom-lpg.c
> +++ b/drivers/leds/rgb/leds-qcom-lpg.c
> @@ -80,58 +80,8 @@
>  #define SDAM_PAUSE_HI_MULTIPLIER_OFFSET	0x8
>  #define SDAM_PAUSE_LO_MULTIPLIER_OFFSET	0x9
>  
> -struct lpg_channel;
>  struct lpg_data;
>  
> -/**
> - * struct lpg - LPG device context
> - * @dev:	pointer to LPG device
> - * @map:	regmap for register access
> - * @lock:	used to synchronize LED and pwm callback requests
> - * @pwm:	PWM-chip object, if operating in PWM mode
> - * @data:	reference to version specific data
> - * @lut_base:	base address of the LUT block (optional)
> - * @lut_size:	number of entries in the LUT block
> - * @lut_bitmap:	allocation bitmap for LUT entries
> - * @pbs_dev:	PBS device
> - * @lpg_chan_sdam:	LPG SDAM peripheral device
> - * @lut_sdam:	LUT SDAM peripheral device
> - * @pbs_en_bitmap:	bitmap for tracking PBS triggers
> - * @triled_base: base address of the TRILED block (optional)
> - * @triled_src:	power-source for the TRILED
> - * @triled_has_atc_ctl:	true if there is TRI_LED_ATC_CTL register
> - * @triled_has_src_sel:	true if there is TRI_LED_SRC_SEL register
> - * @channels:	list of PWM channels
> - * @num_channels: number of @channels
> - */
> -struct lpg {
> -	struct device *dev;
> -	struct regmap *map;
> -
> -	struct mutex lock;
> -
> -	struct pwm_chip *pwm;
> -
> -	const struct lpg_data *data;
> -
> -	u32 lut_base;
> -	u32 lut_size;
> -	unsigned long *lut_bitmap;
> -
> -	struct pbs_dev *pbs_dev;
> -	struct nvmem_device *lpg_chan_sdam;
> -	struct nvmem_device *lut_sdam;
> -	unsigned long pbs_en_bitmap;
> -
> -	u32 triled_base;
> -	u32 triled_src;
> -	bool triled_has_atc_ctl;
> -	bool triled_has_src_sel;
> -
> -	struct lpg_channel *channels;
> -	unsigned int num_channels;
> -};
> -
>  /**
>   * struct lpg_channel - per channel data
>   * @lpg:	reference to parent lpg
> @@ -216,6 +166,55 @@ struct lpg_led {
>  	struct lpg_channel *channels[] __counted_by(num_channels);
>  };
>  
> +/**
> + * struct lpg - LPG device context
> + * @dev:	pointer to LPG device
> + * @map:	regmap for register access
> + * @lock:	used to synchronize LED and pwm callback requests
> + * @pwm:	PWM-chip object, if operating in PWM mode
> + * @data:	reference to version specific data
> + * @lut_base:	base address of the LUT block (optional)
> + * @lut_size:	number of entries in the LUT block
> + * @lut_bitmap:	allocation bitmap for LUT entries
> + * @pbs_dev:	PBS device
> + * @lpg_chan_sdam:	LPG SDAM peripheral device
> + * @lut_sdam:	LUT SDAM peripheral device
> + * @pbs_en_bitmap:	bitmap for tracking PBS triggers
> + * @triled_base: base address of the TRILED block (optional)
> + * @triled_src:	power-source for the TRILED
> + * @triled_has_atc_ctl:	true if there is TRI_LED_ATC_CTL register
> + * @triled_has_src_sel:	true if there is TRI_LED_SRC_SEL register
> + * @channels:	list of PWM channels
> + * @num_channels: number of @channels
> + */

Should we be reordering the kerneldoc descriptions for '@channels' and
'@num_channels' here to correctly match the updated order in the struct below?

> +struct lpg {
> +	struct device *dev;
> +	struct regmap *map;
> +
> +	struct mutex lock;
> +
> +	struct pwm_chip *pwm;
> +
> +	const struct lpg_data *data;
> +
> +	u32 lut_base;
> +	u32 lut_size;
> +	unsigned long *lut_bitmap;
> +
> +	struct pbs_dev *pbs_dev;
> +	struct nvmem_device *lpg_chan_sdam;
> +	struct nvmem_device *lut_sdam;
> +	unsigned long pbs_en_bitmap;
> +
> +	u32 triled_base;
> +	u32 triled_src;
> +	bool triled_has_atc_ctl;
> +	bool triled_has_src_sel;
> +
> +	unsigned int num_channels;
> +	struct lpg_channel channels[] __counted_by(num_channels);
> +};
> +
>  /**
>   * struct lpg_channel_data - per channel initialization data
>   * @sdam_offset:	Channel offset in LPG SDAM
> @@ -1475,12 +1474,6 @@ static int lpg_init_channels(struct lpg *lpg)
>  	struct lpg_channel *chan;
>  	int i;
>  
> -	lpg->num_channels = data->num_channels;
> -	lpg->channels = devm_kcalloc(lpg->dev, data->num_channels,
> -				     sizeof(struct lpg_channel), GFP_KERNEL);
> -	if (!lpg->channels)
> -		return -ENOMEM;
> -
>  	for (i = 0; i < data->num_channels; i++) {
>  		chan = &lpg->channels[i];
>  
> @@ -1603,18 +1596,20 @@ static int lpg_init_sdam(struct lpg *lpg)
>  
>  static int lpg_probe(struct platform_device *pdev)
>  {
> +	const struct lpg_data *data;
>  	struct lpg *lpg;
>  	int ret;
>  	int i;
>  
> -	lpg = devm_kzalloc(&pdev->dev, sizeof(*lpg), GFP_KERNEL);
> +	data = of_device_get_match_data(&pdev->dev);
> +	if (!data)
> +		return -EINVAL;
> +
> +	lpg = devm_kzalloc(&pdev->dev, struct_size(lpg, channels, data->num_channels), GFP_KERNEL);
>  	if (!lpg)
>  		return -ENOMEM;
>  
> -	lpg->data = of_device_get_match_data(&pdev->dev);

You just NULL-ptr-derefed yourself.  Did you test this?

> -	if (!lpg->data)
> -		return -EINVAL;
> -
> +	lpg->num_channels = data->num_channels;
>  	lpg->dev = &pdev->dev;
>  	mutex_init(&lpg->lock);
>  
> -- 
> 2.53.0
> 
> 

-- 
Lee Jones [李琼斯]