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Subject: Re: [PATCH v2 1/1] iio: common: cros_ec_sensors: determine protocol
 version
To:     Fabien Lahoudere <fabien.lahoudere@collabora.com>
Cc:     gwendal@chromium.org, egranata@chromium.org, kernel@collabora.com,
        Nick Vaccaro <nvaccaro@chromium.org>,
        Jonathan Cameron <jic23@kernel.org>,
        Hartmut Knaack <knaack.h@gmx.de>,
        Lars-Peter Clausen <lars@metafoo.de>,
        Peter Meerwald-Stadler <pmeerw@pmeerw.net>,
        Benson Leung <bleung@chromium.org>,
        Guenter Roeck <groeck@chromium.org>,
        Alexios Zavras <alexios.zavras@intel.com>,
        Allison Randal <allison@lohutok.net>,
        Thomas Gleixner <tglx@linutronix.de>,
        Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        linux-iio@vger.kernel.org, linux-kernel@vger.kernel.org
References: <cover.1561731659.git.fabien.lahoudere@collabora.com>
 <f5e824de2c423b310c4981b723bba4945a6512d4.1561731659.git.fabien.lahoudere@collabora.com>
From:   Enric Balletbo i Serra <enric.balletbo@collabora.com>
Message-ID: <4f79e029-b708-11f5-d4c6-2760e0b694d5@collabora.com>
Date:   Fri, 28 Jun 2019 17:13:35 +0200
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Hi,

Thanks for the quick respin, two few comments below

On 28/6/19 16:41, Fabien Lahoudere wrote:
> This patch adds a function to determine which version of the
> protocol is used to communicate with EC.
> 
> Signed-off-by: Fabien Lahoudere <fabien.lahoudere@collabora.com>
> Signed-off-by: Nick Vaccaro <nvaccaro@chromium.org>

The order must be the opposite, first Nick and then you.

> ---
>  .../cros_ec_sensors/cros_ec_sensors_core.c    | 40 ++++++++++++++++++-
>  1 file changed, 39 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/iio/common/cros_ec_sensors/cros_ec_sensors_core.c b/drivers/iio/common/cros_ec_sensors/cros_ec_sensors_core.c
> index 130362ca421b..75d9b617f6c8 100644
> --- a/drivers/iio/common/cros_ec_sensors/cros_ec_sensors_core.c
> +++ b/drivers/iio/common/cros_ec_sensors/cros_ec_sensors_core.c
> @@ -25,6 +25,35 @@ static char *cros_ec_loc[] = {
>  	[MOTIONSENSE_LOC_MAX] = "unknown",
>  };
>  
> +static int cros_ec_get_host_cmd_version_mask(struct cros_ec_device *ec_dev,
> +					     u16 cmd_offset, u16 cmd, u32 *mask)
> +{
> +	int ret;
> +	struct {
> +		struct cros_ec_command msg;
> +		union {
> +			struct ec_params_get_cmd_versions params;
> +			struct ec_response_get_cmd_versions resp;
> +		};
> +	} __packed buf = {
> +		.msg = {
> +			.version = 0,
> +			.command = EC_CMD_GET_CMD_VERSIONS + cmd_offset,
> +			.insize = sizeof(struct ec_response_get_cmd_versions),
> +			.outsize = sizeof(struct ec_params_get_cmd_versions)
> +			},
> +		.params = {.cmd = cmd}
> +	};
> +
> +	ret = cros_ec_cmd_xfer_status(ec_dev, &buf.msg);
> +	if (ret < 0)
> +		return ret;
> +
> +	*mask = buf.resp.version_mask;
> +
> +	return 0;
> +}
> +
>  int cros_ec_sensors_core_init(struct platform_device *pdev,
>  			      struct iio_dev *indio_dev,
>  			      bool physical_device)
> @@ -33,6 +62,8 @@ int cros_ec_sensors_core_init(struct platform_device *pdev,
>  	struct cros_ec_sensors_core_state *state = iio_priv(indio_dev);
>  	struct cros_ec_dev *ec = dev_get_drvdata(pdev->dev.parent);
>  	struct cros_ec_sensor_platform *sensor_platform = dev_get_platdata(dev);
> +	u32 ver_mask;

If you follow the error path in the cros_ec_get_host_cmd_version_mask there is a
possible use of an uninitialized variable.

	u32 ver_mask = 0;

> +	int ret;
>  
>  	platform_set_drvdata(pdev, indio_dev);
>  
> @@ -47,8 +78,15 @@ int cros_ec_sensors_core_init(struct platform_device *pdev,
>  
>  	mutex_init(&state->cmd_lock);
>  

What about adding a comment to explain the ver_mask thing for the record?

	/*
	 * If the EC is very old or misbehaving is it possible that the
	 * communication succeed and have the version mask set to an invalid
	 * value. So check that version mask is valid (!= 0), otherwise return
	 * an error.
	 */

At least this is what I understood from the previous discussion.

> +	ret = cros_ec_get_host_cmd_version_mask(state->ec,
> +						ec->cmd_offset,
> +						EC_CMD_MOTION_SENSE_CMD,
> +						&ver_mask);
> +	if (ret < 0 || ver_mask == 0)
> +		return -ENODEV;
> +
>  	/* Set up the host command structure. */
> -	state->msg->version = 2;
> +	state->msg->version = fls(ver_mask) - 1;;
>  	state->msg->command = EC_CMD_MOTION_SENSE_CMD + ec->cmd_offset;
>  	state->msg->outsize = sizeof(struct ec_params_motion_sense);
>  
> 

Thanks,
~ Enric