[PATCH v7 01/21] net/cpfl: support device initialization

[Ferruh Yigit]

On 2/16/2023 12:29 AM, Mingxia Liu wrote:
> +static int
> +cpfl_dev_configure(struct rte_eth_dev *dev)
> +{
> +	struct rte_eth_conf *conf = &dev->data->dev_conf;
> +
> +	if (conf->link_speeds & RTE_ETH_LINK_SPEED_FIXED) {
> +		PMD_INIT_LOG(ERR, "Setting link speed is not supported");
> +		return -ENOTSUP;
> +	}
> +
> +	if (conf->txmode.mq_mode != RTE_ETH_MQ_TX_NONE) {
> +		PMD_INIT_LOG(ERR, "Multi-queue TX mode %d is not supported",
> +			     conf->txmode.mq_mode);
> +		return -ENOTSUP;
> +	}
> +
> +	if (conf->lpbk_mode != 0) {
> +		PMD_INIT_LOG(ERR, "Loopback operation mode %d is not supported",
> +			     conf->lpbk_mode);
> +		return -ENOTSUP;
> +	}
> +
> +	if (conf->dcb_capability_en != 0) {
> +		PMD_INIT_LOG(ERR, "Priority Flow Control(PFC) if not supported");
> +		return -ENOTSUP;
> +	}
> +
> +	if (conf->intr_conf.lsc != 0) {
> +		PMD_INIT_LOG(ERR, "LSC interrupt is not supported");
> +		return -ENOTSUP;
> +	}
> +
> +	if (conf->intr_conf.rxq != 0) {
> +		PMD_INIT_LOG(ERR, "RXQ interrupt is not supported");
> +		return -ENOTSUP;
> +	}
> +
> +	if (conf->intr_conf.rmv != 0) {
> +		PMD_INIT_LOG(ERR, "RMV interrupt is not supported");
> +		return -ENOTSUP;
> +	}
> +
> +	return 0;

This is '.dev_configure()' dev ops of a driver, there is nothing wrong
with the function but it is a good example to highlight a point.


'rte_eth_dev_configure()' can fail from various reasons, what can an
application do in this case?
It is not clear why configuration failed, there is no way to figure out
failed config option dynamically.

Application developer can read the log and find out what caused the
failure, but what can do next? Put a conditional check for the
particular device, assuming application supports multiple devices,
before configuration?

I think we need better error value, to help application detect what went
wrong and adapt dynamically, perhaps a bitmask of errors one per each
config option, what do you think?



And I think this is another reason why we should not make a single API
too overloaded and complex.