linux-kernel - Re: [PATCH] platform/chrome: cros_ec_proto: Fix check

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Date:   Tue, 21 Sep 2021 13:42:04 +0200
From:   Enric Balletbo i Serra <enric.balletbo@...labora.com>
To:     Prashant Malani <pmalani@...omium.org>,
        linux-kernel@...r.kernel.org
Cc:     Benson Leung <bleung@...omium.org>,
        Guenter Roeck <groeck@...omium.org>,
        "Gustavo A. R. Silva" <gustavoars@...nel.org>
Subject: Re: [PATCH] platform/chrome: cros_ec_proto: Fix check_features ret
 val

Hi Prashant,

Thank you for the patch. Just one comment below ...

On 16/9/21 3:46, Prashant Malani wrote:
> The kerneldoc for cros_ec_check_features() states that it returns 1 or 0
> depedending on whether a feature is supported or not, but it instead
> returns a negative error number in one case, and a non-1 bitmask in
> other cases.
> 
> Since all call-sites only check for a 1 or 0 return value, update
> the function to return boolean values.
> 
> Signed-off-by: Prashant Malani <pmalani@...omium.org>
> ---
>  drivers/platform/chrome/cros_ec_proto.c     | 12 +++++++-----
>  include/linux/platform_data/cros_ec_proto.h |  2 +-
>  2 files changed, 8 insertions(+), 6 deletions(-)
> 
> diff --git a/drivers/platform/chrome/cros_ec_proto.c b/drivers/platform/chrome/cros_ec_proto.c
> index a7404d69b2d3..a34cf58c5ef7 100644
> --- a/drivers/platform/chrome/cros_ec_proto.c
> +++ b/drivers/platform/chrome/cros_ec_proto.c
> @@ -808,9 +808,9 @@ EXPORT_SYMBOL(cros_ec_get_host_event);
>   *
>   * Call this function to test whether the ChromeOS EC supports a feature.
>   *
> - * Return: 1 if supported, 0 if not
> + * Return: true if supported, false if not (or if an error was encountered).
>   */
> -int cros_ec_check_features(struct cros_ec_dev *ec, int feature)
> +bool cros_ec_check_features(struct cros_ec_dev *ec, int feature)
>  {
>  	struct cros_ec_command *msg;
>  	int ret;
> @@ -818,8 +818,10 @@ int cros_ec_check_features(struct cros_ec_dev *ec, int feature)
>  	if (ec->features[0] == -1U && ec->features[1] == -1U) {
>  		/* features bitmap not read yet */
>  		msg = kzalloc(sizeof(*msg) + sizeof(ec->features), GFP_KERNEL);
> -		if (!msg)
> -			return -ENOMEM;
> +		if (!msg) {
> +			dev_err(ec->dev, "failed to allocate memory to get EC features\n");

In case of failure you will be noticed by the allocator, prints after
[k|v][m|z|c]alloc() functions are not needed, so I think you can just return
false here.

Other than that the patch looks good to me.

Thanks,
  Enric

> +			return false;
> +		}
>  
>  		msg->command = EC_CMD_GET_FEATURES + ec->cmd_offset;
>  		msg->insize = sizeof(ec->features);
> @@ -839,7 +841,7 @@ int cros_ec_check_features(struct cros_ec_dev *ec, int feature)
>  		kfree(msg);
>  	}
>  
> -	return ec->features[feature / 32] & EC_FEATURE_MASK_0(feature);
> +	return !!(ec->features[feature / 32] & EC_FEATURE_MASK_0(feature));
>  }
>  EXPORT_SYMBOL_GPL(cros_ec_check_features);
>  
> diff --git a/include/linux/platform_data/cros_ec_proto.h b/include/linux/platform_data/cros_ec_proto.h
> index 02599687770c..55844ece0b32 100644
> --- a/include/linux/platform_data/cros_ec_proto.h
> +++ b/include/linux/platform_data/cros_ec_proto.h
> @@ -227,7 +227,7 @@ int cros_ec_get_next_event(struct cros_ec_device *ec_dev,
>  
>  u32 cros_ec_get_host_event(struct cros_ec_device *ec_dev);
>  
> -int cros_ec_check_features(struct cros_ec_dev *ec, int feature);
> +bool cros_ec_check_features(struct cros_ec_dev *ec, int feature);
>  
>  int cros_ec_get_sensor_count(struct cros_ec_dev *ec);
>  
>