Re: [PATCH] v2 bakclight: fix missing checks in ambient_light_zone_store

From: Daniel Thompson <daniel.thompson@linaro.org>
To: Aditya Pakki <pakki001@umn.edu>
Cc: kjlu@umn.edu, Lee Jones <lee.jones@linaro.org>,
	Jingoo Han <jingoohan1@gmail.com>,
	Bartlomiej Zolnierkiewicz <b.zolnierkie@samsung.com>,
	dri-devel@lists.freedesktop.org, linux-fbdev@vger.kernel.org,
	linux-kernel@vger.kernel.org
Subject: Re: [PATCH] v2 bakclight: fix missing checks in ambient_light_zone_store
Date: Mon, 7 Jan 2019 11:12:14 +0000	[thread overview]
Message-ID: <20190107111214.hl3issz5yzs5muqc@holly.lan> (raw)
In-Reply-To: <20190105184807.4827-1-pakki001@umn.edu>

On Sat, Jan 05, 2019 at 12:48:07PM -0600, Aditya Pakki wrote:
> In adp8870_bl_ambient_light_zone_store, set, clear, and write

I'm curious...

What attracted you to this particular _store function? AFAICT the same
ignoring of return values occurs in other _store functions in this file?

> can return an error but are not checked. The fix adds a check for these
> cases and returns -1 to match the return type (ssize_t).

This isn't right. The caller of the store function expects -errno
values (this is the default for almost all kernel functions).

> Signed-off-by: Aditya Pakki <pakki001@umn.edu>
> ---
>  drivers/video/backlight/adp8870_bl.c | 16 +++++++++++++---
>  1 file changed, 13 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/video/backlight/adp8870_bl.c b/drivers/video/backlight/adp8870_bl.c
> index 8d50e0299578..56a640587a82 100644
> --- a/drivers/video/backlight/adp8870_bl.c
> +++ b/drivers/video/backlight/adp8870_bl.c
> @@ -800,10 +800,14 @@ static ssize_t adp8870_bl_ambient_light_zone_store(struct device *dev,
>  
>  	if (val == 0) {
>  		/* Enable automatic ambient light sensing */
> -		adp8870_set_bits(data->client, ADP8870_MDCR, CMP_AUTOEN);
> +		ret = adp8870_set_bits(data->client, ADP8870_MDCR, CMP_AUTOEN);
> +		if (ret < 0)
> +			goto adp8870_bl_err;

There's nothing *wrong* with goto for error handling but is it
really needed here (there is no recovery code)?

>  	} else if ((val > 0) && (val < 6)) {
>  		/* Disable automatic ambient light sensing */
> -		adp8870_clr_bits(data->client, ADP8870_MDCR, CMP_AUTOEN);
> +		ret = adp8870_clr_bits(data->client, ADP8870_MDCR, CMP_AUTOEN);
> +		if (ret < 0)
> +			goto adp8870_bl_err;

+1

>  
>  		/* Set user supplied ambient light zone */
>  		mutex_lock(&data->lock);
> @@ -811,12 +815,18 @@ static ssize_t adp8870_bl_ambient_light_zone_store(struct device *dev,
>  		if (!ret) {
>  			reg_val &= ~(CFGR_BLV_MASK << CFGR_BLV_SHIFT);
>  			reg_val |= (val - 1) << CFGR_BLV_SHIFT;
> -			adp8870_write(data->client, ADP8870_CFGR, reg_val);
> +			ret = adp8870_write(data->client, ADP8870_CFGR,
> +						reg_val);
>  		}
>  		mutex_unlock(&data->lock);
> +		if (ret < 0)
> +			goto adp8870_bl_err;

+1

Daniel.

>  	}
>  
>  	return count;
> +
> +adp8870_bl_err:
> +	return -1;
>  }
>  static DEVICE_ATTR(ambient_light_zone, 0664,
>  		adp8870_bl_ambient_light_zone_show,
> -- 
> 2.17.1
> 