ethdev: avoid usage of uninit device info in bad port case

  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.

Fixes: a30268e9a2d0 ("ethdev: reset whole dev info structure before filling")
Cc: stable@dpdk.org

Signed-off-by: Andrew Rybchenko <arybchenko@solarflare.com>
---
 lib/librte_ethdev/rte_ethdev.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)
  

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@dpdk.org
> 
> Signed-off-by: Andrew Rybchenko <arybchenko@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;
>
  

On 7/23/19 1:40 PM, Ferruh Yigit wrote:
> 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.

Thomas, what do you think? Should we finally fix it?
I think it is almost harmless API/ABI breakage.
If yes, I'll send deprecation notice to do it in v19.11.

> 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?

See v2.
  

23/07/2019 14:16, Andrew Rybchenko:
> On 7/23/19 1:40 PM, Ferruh Yigit wrote:
> > 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.
> 
> Thomas, what do you think? Should we finally fix it?
> I think it is almost harmless API/ABI breakage.
> If yes, I'll send deprecation notice to do it in v19.11.

Yes, generally speaking we should not have any void return in API.