Re: [PATCH] mfd: cros_ec: Read EC features during probe to catch transfer error

On Fri, 22 May 2026, Andrei Kuchynski wrote:

> cros_ec_check_features() does not return an error if the underlying
> EC_CMD_GET_FEATURES command fails. Consequently, when the Fingerprint
> device fails to respond, the probe function ignores the failure and falls
> back to installing it as 'cros_ec' device instead of 'cros_fp'.
> This leads to a sysfs duplicate filename collision later when the real
> 'cros_ec' device attempts to register:
> 
>   cros-ec-spi spi5.0: EC failed to respond in time
>   cros-ec-dev.19.auto: cannot get EC features: -110
>   sysfs : cannot create duplicate filename '/class/chromeos/cros_ec'
>         : sysfs_do_create_link_sd+0x94/0xdc
>         : ec_device_probe+0x150/0x4f0
> 
> Fix this by extracting the feature reading logic into a new helper function
> cros_ec_read_features() and calling it during ec_device_probe().
> If the transfer fails, abort the broken device initialization.

You're doing 2 things here.  Move the function first, then add the new
call into MFD in a subsequent patch.

> Signed-off-by: Andrei Kuchynski <[email protected]>
> ---
>  drivers/mfd/cros_ec_dev.c                   |  4 +++
>  drivers/platform/chrome/cros_ec_proto.c     | 30 +++++++++++++++------
>  include/linux/platform_data/cros_ec_proto.h |  2 ++
>  3 files changed, 28 insertions(+), 8 deletions(-)
> 
> diff --git a/drivers/mfd/cros_ec_dev.c b/drivers/mfd/cros_ec_dev.c
> index 39430dd44e30c..7810b1c871849 100644
> --- a/drivers/mfd/cros_ec_dev.c
> +++ b/drivers/mfd/cros_ec_dev.c
> @@ -203,6 +203,10 @@ static int ec_device_probe(struct platform_device *pdev)
>  	ec->features.flags[1] = -1U; /* Not cached yet */
>  	device_initialize(&ec->class_dev);
>  
> +	retval = cros_ec_read_features(ec);
> +	if (retval < 0)
> +		return retval;

You just leaked ec->class_dev.

	goto failed;  ?

> +
>  	for (i = 0; i < ARRAY_SIZE(cros_mcu_devices); i++) {
>  		/*
>  		 * Check whether this is actually a dedicated MCU rather
> diff --git a/drivers/platform/chrome/cros_ec_proto.c b/drivers/platform/chrome/cros_ec_proto.c
> index 1d8d9168ec1aa..724d1313f6b21 100644
> --- a/drivers/platform/chrome/cros_ec_proto.c
> +++ b/drivers/platform/chrome/cros_ec_proto.c
> @@ -946,6 +946,27 @@ u32 cros_ec_get_host_event(struct cros_ec_device *ec_dev)
>  }
>  EXPORT_SYMBOL(cros_ec_get_host_event);
>  
> +/**
> + * cros_ec_read_features() - Read EC features
> + *
> + * @ec: EC device.
> + *
> + * Return: >= 0 on success, negative error number on failure.
> + */
> +int cros_ec_read_features(struct cros_ec_dev *ec)
> +{
> +	int ret = cros_ec_cmd(ec->ec_dev, 0, EC_CMD_GET_FEATURES + ec->cmd_offset,
> +			      NULL, 0, &ec->features, sizeof(ec->features));
> +
> +	if (ret < 0) {
> +		dev_warn(ec->dev, "cannot get EC features: %d\n", ret);
> +		memset(&ec->features, 0, sizeof(ec->features));
> +	}
> +
> +	return ret;
> +}
> +EXPORT_SYMBOL_GPL(cros_ec_read_features);
> +
>  /**
>   * cros_ec_check_features() - Test for the presence of EC features
>   *
> @@ -960,17 +981,10 @@ EXPORT_SYMBOL(cros_ec_get_host_event);
>  bool cros_ec_check_features(struct cros_ec_dev *ec, int feature)
>  {
>  	struct ec_response_get_features *features = &ec->features;
> -	int ret;
>  
>  	if (features->flags[0] == -1U && features->flags[1] == -1U) {
>  		/* features bitmap not read yet */
> -		ret = cros_ec_cmd(ec->ec_dev, 0, EC_CMD_GET_FEATURES + ec->cmd_offset,
> -				  NULL, 0, features, sizeof(*features));
> -		if (ret < 0) {
> -			dev_warn(ec->dev, "cannot get EC features: %d\n", ret);
> -			memset(features, 0, sizeof(*features));
> -		}
> -
> +		cros_ec_read_features(ec);
>  		dev_dbg(ec->dev, "EC features %08x %08x\n",
>  			features->flags[0], features->flags[1]);
>  	}
> diff --git a/include/linux/platform_data/cros_ec_proto.h b/include/linux/platform_data/cros_ec_proto.h
> index 6ed1c4c5ce2ef..a1ccecf5e1f83 100644
> --- a/include/linux/platform_data/cros_ec_proto.h
> +++ b/include/linux/platform_data/cros_ec_proto.h
> @@ -271,6 +271,8 @@ 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_read_features(struct cros_ec_dev *ec);
> +
>  bool cros_ec_check_features(struct cros_ec_dev *ec, int feature);
>  
>  int cros_ec_get_sensor_count(struct cros_ec_dev *ec);
> -- 
> 2.54.0.746.g67dd491aae-goog
> 

-- 
Lee Jones