linux-kernel - Re: [PATCH] leds: mt6360: Fix the second LED can not enable torch mode by V4L2

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Date: Tue, 9 Apr 2024 13:45:41 +0200
From: AngeloGioacchino Del Regno <angelogioacchino.delregno@...labora.com>
To: ChiaEn Wu <chiaen_wu@...htek.com>, pavel@....cz, lee@...nel.org,
 matthias.bgg@...il.com
Cc: linux-kernel@...r.kernel.org, linux-leds@...r.kernel.org,
 linux-arm-kernel@...ts.infradead.org, linux-mediatek@...ts.infradead.org,
 peterwu.pub@...il.com, cy_huang@...htek.com
Subject: Re: [PATCH] leds: mt6360: Fix the second LED can not enable torch
 mode by V4L2

Il 09/04/24 12:21, ChiaEn Wu ha scritto:
> V4L2 will disable strobe mode of the LED device when enable torch mode,
> but this logic will conflict with the "priv->fled_torch_used"
> in "mt6360_strobe_set()". So after enabling torch mode of the first
> LED, the second LED will not be able to enable torch mode correctly.
> 
> Therefore, at the beginning of "mt6360_strobe_set()", check whether the
> state of the upcoming change and the current LED device state are the
> same, so as to avoid the above problem.
> 
> Signed-off-by: ChiaEn Wu <chiaen_wu@...htek.com>
> ---
>   drivers/leds/flash/leds-mt6360.c | 12 +++++++++++-
>   1 file changed, 11 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/leds/flash/leds-mt6360.c b/drivers/leds/flash/leds-mt6360.c
> index a90de82f4568..1b75b4d36834 100644
> --- a/drivers/leds/flash/leds-mt6360.c
> +++ b/drivers/leds/flash/leds-mt6360.c
> @@ -241,10 +241,20 @@ static int mt6360_strobe_set(struct led_classdev_flash *fl_cdev, bool state)
>   	u32 enable_mask = MT6360_STROBEN_MASK | MT6360_FLCSEN_MASK(led->led_no);
>   	u32 val = state ? MT6360_FLCSEN_MASK(led->led_no) : 0;
>   	u32 prev = priv->fled_strobe_used, curr;
> -	int ret;
> +	int ret = 0;

I prefer that you leave ret uninitialized here, and...

>   
>   	mutex_lock(&priv->lock);
>   
> +	/*
> +	 * If the state of the upcoming change is the same as the current LED
> +	 * device state, then skip the subsequent code to avoid conflict
> +	 * with the flow of turning on LED torch mode in V4L2.
> +	 */
> +	if (state == !!(BIT(led->led_no) & prev)) {
> +		dev_info(lcdev->dev, "No change in strobe state [0x%x]\n", prev);

..that you do here, instead

		ret = 0;
		goto unlock;

With that addressed,

Reviewed-by: AngeloGioacchino Del Regno <angelogioacchino.delregno@...laobra.com>