[dpdk-dev] [PATCH] ethdev: avoid usage of uninit device info in bad port case

[Ferruh Yigit]

On 7/23/2019 10:13 AM, Andrew Rybchenko wrote:
> rte_eth_dev_info_get() returns void and caller does know if the function
> does its job or not. Changing of the return value to int would be
> API/ABI breakage which requires deprecation process and cannot be
> backported to stable branches. For now, make sure that device info is
> initialized even in the case of invalid port ID.

+1 to return a status from function for long term.

But someone looks below code can think we are doing an unnecessary memset for
the error case, and will fix it :)
What do you think adding a comment to prevent this?

> 
> Fixes: a30268e9a2d0 ("ethdev: reset whole dev info structure before filling")
> Cc: stable at dpdk.org
> 
> Signed-off-by: Andrew Rybchenko <arybchenko at solarflare.com>
> ---
>  lib/librte_ethdev/rte_ethdev.c | 3 ++-
>  1 file changed, 2 insertions(+), 1 deletion(-)
> 
> diff --git a/lib/librte_ethdev/rte_ethdev.c b/lib/librte_ethdev/rte_ethdev.c
> index 64191737c..97b093edc 100644
> --- a/lib/librte_ethdev/rte_ethdev.c
> +++ b/lib/librte_ethdev/rte_ethdev.c
> @@ -2552,10 +2552,11 @@ rte_eth_dev_info_get(uint16_t port_id, struct rte_eth_dev_info *dev_info)
>  		.nb_mtu_seg_max = UINT16_MAX,
>  	};
>  
> +	memset(dev_info, 0, sizeof(struct rte_eth_dev_info));
> +
>  	RTE_ETH_VALID_PORTID_OR_RET(port_id);
>  	dev = &rte_eth_devices[port_id];
>  
> -	memset(dev_info, 0, sizeof(struct rte_eth_dev_info));
>  	dev_info->rx_desc_lim = lim;
>  	dev_info->tx_desc_lim = lim;
>  	dev_info->device = dev->device;
>