Re: [dpdk-dev] [PATCH v2] ethdev: Rename RX/TX enable queue field for queue start and stop

[Thomas Monjalon <thomas.monjalon@6wind.com>]

Hi Ouyang,

2014-07-23 12:48, Ouyang Changchun:
> Update comments for the field start_rx_per_q for better readability.
> Rename the field name to rx_enable_queue for better readability too.
> Accordingly Update its reference in sample vhost.

> -	uint8_t start_rx_per_q; /**< start rx per queue. */
> +	/**< If rx_enable_queue is true, rte_eth_dev_rx_queue_start should be
> +		invocated to start RX for one queue after rte_eth_dev_start is
> +		invocated, and rte_eth_dev_rx_queue_start instead of
> +		rte_eth_dev_start is responsible for allocating mbuf from
> +		mempool and setup the DMA physical address. It is useful in
> +		such scenario: buffer address is not available at the point of
> +		rte_eth_dev_start's invocating but available later, e.g. in
> +		VHOST zero copy case, the buffer address used to setup DMA
> +		address is available only after one VM(guest) startup. */
> +	uint8_t rx_enable_queue;
>  };

I have many comments here.

The doxygen comment /**< must be used only after the symbol you are
commenting:
	http://doxygen.org/manual/docblocks.html#memberdoc

The comment is too long.
The use case would be in the manual, not in doxygen.
The comment about rte_eth_dev_rx_queue_start would be in the doxygen
comment of rte_eth_dev_rx_queue_start.

When this variable is set, it doesn't enable anything. It only disables
the queue when doing a global start. Its name should be rx_deferred_start.
All fields of this structure are about one queue, so the "queue" word is
not needed.

> -	uint8_t start_tx_per_q; /**< start tx per queue. */
> +	/**< If tx_enable_queue is true, rte_eth_dev_tx_queue_start must be
> +		invocated to start TX for one queue after rte_eth_dev_start is
> +		invocated. Refer to start_rx_per_q for the use case. */
> +	uint8_t tx_enable_queue;
>  };

You refer to the old name (start_rx_per_q).
By the way, a one line description (without referral) for both fields should
be enough. Something like "do not start with rte_eth_dev_start()".

> @@ -3652,13 +3652,13 @@ ixgbe_dev_rxtx_start(struct rte_eth_dev *dev)
>  
>  	for (i = 0; i < dev->data->nb_tx_queues; i++) {
>  		txq = dev->data->tx_queues[i];
> -		if (!txq->start_tx_per_q)
> +		if (!txq->tx_enable_queue)
>  			ixgbe_dev_tx_queue_start(dev, i);
>  	}

Here it's clear that this field is about disabling start.

Please rework this patch and update i40e accordingly.
Thanks
-- 
Thomas