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

Lee Jones
2026-04-09T15:12:57Z

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]