linux-kernel - Re: [PATCH 02/10] backlight: qcom-wled: Use cpu_to

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Message-ID: <20211005090659.rt4bxlkvbabwsiru@maple.lan>
Date:   Tue, 5 Oct 2021 10:06:59 +0100
From:   Daniel Thompson <daniel.thompson@...aro.org>
To:     Marijn Suijten <marijn.suijten@...ainline.org>
Cc:     phone-devel@...r.kernel.org, Andy Gross <agross@...nel.org>,
        Bjorn Andersson <bjorn.andersson@...aro.org>,
        Lee Jones <lee.jones@...aro.org>,
        Jingoo Han <jingoohan1@...il.com>,
        ~postmarketos/upstreaming@...ts.sr.ht,
        AngeloGioacchino Del Regno 
        <angelogioacchino.delregno@...ainline.org>,
        Konrad Dybcio <konrad.dybcio@...ainline.org>,
        Martin Botka <martin.botka@...ainline.org>,
        Jami Kettunen <jami.kettunen@...ainline.org>,
        Pavel Dubrova <pashadubrova@...il.com>,
        Kiran Gunda <kgunda@...eaurora.org>,
        Courtney Cavin <courtney.cavin@...ymobile.com>,
        Bryan Wu <cooloney@...il.com>, linux-arm-msm@...r.kernel.org,
        dri-devel@...ts.freedesktop.org, linux-fbdev@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH 02/10] backlight: qcom-wled: Use cpu_to_le16 macro to
 perform conversion

On Mon, Oct 04, 2021 at 09:27:33PM +0200, Marijn Suijten wrote:
> The kernel already provides appropriate primitives to perform endianness
> conversion which should be used in favour of manual bit-wrangling.
> 
> Signed-off-by: Marijn Suijten <marijn.suijten@...ainline.org>
> Reviewed-by: AngeloGioacchino Del Regno <angelogioacchino.delregno@...ainline.org>

Reviewed-by: Daniel Thompson <daniel.thompson@...aro.org>


> ---
>  drivers/video/backlight/qcom-wled.c | 25 +++++++++++--------------
>  1 file changed, 11 insertions(+), 14 deletions(-)
> 
> diff --git a/drivers/video/backlight/qcom-wled.c b/drivers/video/backlight/qcom-wled.c
> index 6af808af2328..9927ed98944a 100644
> --- a/drivers/video/backlight/qcom-wled.c
> +++ b/drivers/video/backlight/qcom-wled.c
> @@ -231,14 +231,14 @@ struct wled {
>  static int wled3_set_brightness(struct wled *wled, u16 brightness)
>  {
>  	int rc, i;
> -	u8 v[2];
> +	u16 v;
>  
> -	v[0] = brightness & 0xff;
> -	v[1] = (brightness >> 8) & 0xf;
> +	v = cpu_to_le16(brightness & WLED3_SINK_REG_BRIGHT_MAX);
>  
>  	for (i = 0;  i < wled->cfg.num_strings; ++i) {
>  		rc = regmap_bulk_write(wled->regmap, wled->ctrl_addr +
> -				       WLED3_SINK_REG_BRIGHT(i), v, 2);
> +				       WLED3_SINK_REG_BRIGHT(i),
> +				       &v, sizeof(v));
>  		if (rc < 0)
>  			return rc;
>  	}
> @@ -249,19 +249,18 @@ static int wled3_set_brightness(struct wled *wled, u16 brightness)
>  static int wled4_set_brightness(struct wled *wled, u16 brightness)
>  {
>  	int rc, i;
> -	u16 low_limit = wled->max_brightness * 4 / 1000;
> -	u8 v[2];
> +	u16 v, low_limit = wled->max_brightness * 4 / 1000;
>  
>  	/* WLED4's lower limit of operation is 0.4% */
>  	if (brightness > 0 && brightness < low_limit)
>  		brightness = low_limit;
>  
> -	v[0] = brightness & 0xff;
> -	v[1] = (brightness >> 8) & 0xf;
> +	v = cpu_to_le16(brightness & WLED3_SINK_REG_BRIGHT_MAX);
>  
>  	for (i = 0;  i < wled->cfg.num_strings; ++i) {
>  		rc = regmap_bulk_write(wled->regmap, wled->sink_addr +
> -				       WLED4_SINK_REG_BRIGHT(i), v, 2);
> +				       WLED4_SINK_REG_BRIGHT(i),
> +				       &v, sizeof(v));
>  		if (rc < 0)
>  			return rc;
>  	}
> @@ -272,22 +271,20 @@ static int wled4_set_brightness(struct wled *wled, u16 brightness)
>  static int wled5_set_brightness(struct wled *wled, u16 brightness)
>  {
>  	int rc, offset;
> -	u16 low_limit = wled->max_brightness * 1 / 1000;
> -	u8 v[2];
> +	u16 v, low_limit = wled->max_brightness * 1 / 1000;
>  
>  	/* WLED5's lower limit is 0.1% */
>  	if (brightness < low_limit)
>  		brightness = low_limit;
>  
> -	v[0] = brightness & 0xff;
> -	v[1] = (brightness >> 8) & 0x7f;
> +	v = cpu_to_le16(brightness & WLED5_SINK_REG_BRIGHT_MAX_15B);
>  
>  	offset = (wled->cfg.mod_sel == MOD_A) ?
>  		  WLED5_SINK_REG_MOD_A_BRIGHTNESS_LSB :
>  		  WLED5_SINK_REG_MOD_B_BRIGHTNESS_LSB;
>  
>  	rc = regmap_bulk_write(wled->regmap, wled->sink_addr + offset,
> -			       v, 2);
> +			       &v, sizeof(v));
>  	return rc;
>  }
>  
> -- 
> 2.33.0
>