linux-kernel - Re: [PATCH v6 01/11] platform: chrome: sensorhub: Add FIFO support

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Message-ID: <399a282a-e6a6-a1ed-26c4-1999008f242d@collabora.com>
Date:   Wed, 25 Mar 2020 17:28:05 +0100
From:   Enric Balletbo i Serra <enric.balletbo@...labora.com>
To:     Gwendal Grignou <gwendal@...omium.org>, bleung@...omium.org,
        Jonathan.Cameron@...wei.com
Cc:     linux-iio@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v6 01/11] platform: chrome: sensorhub: Add FIFO support

Hi Gwendal,

Many thanks for sending this series upstream. Just one comment, other than that
looks good to me.

On 24/3/20 21:27, Gwendal Grignou wrote:
> cros_ec_sensorhub registers a listener and query motion sense FIFO,
> spread to iio sensors registers.
> 
> To test, we can use libiio:
> iiod&
> iio_readdev -u ip:localhost -T 10000 -s 25 -b 16 cros-ec-gyro | od -x
> 
> Reviewed-by: Jonathan Cameron <Jonathan.Cameron@...wei.com>
> Signed-off-by: Gwendal Grignou <gwendal@...omium.org>

[snip]

> +/**
> + * cros_ec_sensorhub_ring_handler() - The trigger handler function
> + *
> + * @sensorhub: Sensor Hub object.
> + *
> + * Called by the notifier, process the EC sensor FIFO queue.
> + */
> +static void cros_ec_sensorhub_ring_handler(struct cros_ec_sensorhub *sensorhub)
> +{
> +	struct cros_ec_fifo_info *fifo_info = &sensorhub->fifo_info;
> +	struct cros_ec_dev *ec = sensorhub->ec;
> +	ktime_t fifo_timestamp, current_timestamp;
> +	int i, j, number_data, ret;
> +	unsigned long sensor_mask = 0;
> +	struct ec_response_motion_sensor_data *in;
> +	struct cros_ec_sensors_ring_sample *out, *last_out;
> +
> +	mutex_lock(&sensorhub->cmd_lock);
> +
> +	/* Get FIFO information if there are lost vectors. */
> +	if (fifo_info->info.total_lost) {
> +		/* Need to retrieve the number of lost vectors per sensor */
> +		sensorhub->params->cmd = MOTIONSENSE_CMD_FIFO_INFO;
> +		sensorhub->msg->outsize = 1;
> +		sensorhub->msg->insize =
> +			sizeof(struct ec_response_motion_sense_fifo_info) +
> +			sizeof(u16) * CROS_EC_SENSOR_MAX;
> +
> +		if (cros_ec_cmd_xfer_status(ec->ec_dev, sensorhub->msg) < 0)
> +			goto error;
> +
> +		memcpy(fifo_info, &sensorhub->resp->fifo_info,
> +		       sizeof(*fifo_info));
> +

Smatch is reporting:

cros_ec_sensorhub_ring_handler() error: memcpy() '&sensorhub->resp->fifo_info'
too small (10 vs 42)

Is it fine and safe to copy always the 42 bytes? I suspect that we should only
copy the number of lost events, total_lost , not always the maximum (16). Or the
EC is always sending the full array (16 bytes)?

Thanks,
Enric