Re: [PATCH v3] app/testpmd: support specify TCs when DCB forward

[Stephen Hemminger <stephen@networkplumber.org>]

On Thu, 6 Nov 2025 20:49:59 +0800
Chengwen Feng <fengchengwen@huawei.com> wrote:

> +static void
> +dcb_forward_tc_update_dcb_info(struct rte_eth_dcb_info *org_dcb_info)
> +{
> +	struct rte_eth_dcb_info dcb_info = {0};
> +	uint32_t i, vmdq_idx;
> +	uint32_t tc = 0;
> +
> +	if (dcb_fwd_tc_mask == DEFAULT_DCB_FWD_TC_MASK)
> +		return;
> +
> +	/*
> +	 * Use compress scheme to update dcb-info.
> +	 * E.g. If org_dcb_info->nb_tcs is 4 and dcb_fwd_tc_mask is 0x8, it
> +	 *      means only enable TC3, then the new dcb-info's nb_tcs is set to
> +	 *      1, and also move corresponding tc_rxq and tc_txq info to new
> +	 *      index.
> +	 */
> +	for (i = 0; i < org_dcb_info->nb_tcs; i++) {
> +		if (!(dcb_fwd_tc_mask & (1u << i)))
> +			continue;
> +		for (vmdq_idx = 0; vmdq_idx < RTE_ETH_MAX_VMDQ_POOL; vmdq_idx++) {
> +			dcb_info.tc_queue.tc_rxq[vmdq_idx][tc].base =
> +				org_dcb_info->tc_queue.tc_rxq[vmdq_idx][i].base;
> +			dcb_info.tc_queue.tc_rxq[vmdq_idx][tc].nb_queue =
> +				org_dcb_info->tc_queue.tc_rxq[vmdq_idx][i].nb_queue;
> +			dcb_info.tc_queue.tc_txq[vmdq_idx][tc].base =
> +				org_dcb_info->tc_queue.tc_txq[vmdq_idx][i].base;
> +			dcb_info.tc_queue.tc_txq[vmdq_idx][tc].nb_queue =
> +				org_dcb_info->tc_queue.tc_txq[vmdq_idx][i].nb_queue;
> +		}
> +		tc++;
> +	}
> +	dcb_info.nb_tcs = tc;
> +	memcpy(org_dcb_info, &dcb_info, sizeof(struct rte_eth_dcb_info));

Prefer direct structure assignment over memcpy() here.
	*org_dcb_info = dcb_info;

This makes sure types are the same, and compiler generates same code.