Re: [PATCH v2] app/testpmd: fix lcore ID restriction

[Ferruh Yigit <ferruh.yigit@amd.com>]

On 4/19/2024 12:30 PM, Ferruh Yigit wrote:
> On 4/16/2024 10:55 AM, Sivaprasad Tummala wrote:
>> diff --git a/app/test-pmd/config.c b/app/test-pmd/config.c
>> index ba1007ace6..6b28c22c96 100644
>> --- a/app/test-pmd/config.c
>> +++ b/app/test-pmd/config.c
>> @@ -4785,9 +4785,9 @@ fwd_stream_on_other_lcores(uint16_t domain_id, lcoreid_t src_lc,
>>  				continue;
>>  			printf("Shared Rx queue group %u queue %hu can't be scheduled on different cores:\n",
>>  			       share_group, share_rxq);
>> -			printf("  lcore %hhu Port %hu queue %hu\n",
>> +			printf("  lcore %u Port %hu queue %hu\n",
>>  			       src_lc, src_port, src_rxq);
>> -			printf("  lcore %hhu Port %hu queue %hu\n",
>> +			printf("  lcore %u Port %hu queue %hu\n",
>>  			       lc_id, fs->rx_port, fs->rx_queue);
>>  			printf("Please use --nb-cores=%hu to limit number of forwarding cores\n",
>>  			       nb_rxq);
>> @@ -5159,7 +5159,7 @@ icmp_echo_config_setup(void)
>>  	lcoreid_t lc_id;
>>  	uint16_t  sm_id;
>>  
>> -	if ((nb_txq * nb_fwd_ports) < nb_fwd_lcores)
>> +	if ((lcoreid_t)(nb_txq * nb_fwd_ports) < nb_fwd_lcores)
>>  		cur_fwd_config.nb_fwd_lcores = (lcoreid_t)
>>  			(nb_txq * nb_fwd_ports);
>>
> 
> Hi Sivaprasad,
> 
> Is this '(lcoreid_t)' cast required? Because of integer promotion I
> think result will be correct without casting.
> 
> (And without integer promotion considered, casting needs to be done on
> one of the variables, not to the result, because result may be already
> cast down I think. Anyway this is not required for this case since
> variables are u16.)
>

Why casing required (for record) is,
'nb_txq' -> uint16_t, promoted to 'int'
'nb_fwd_ports' -> uint16_t, promoted to 'int'
(nb_txq * nb_fwd_ports) -> result 'int'
nb_fwd_lcores  -> 'uint32_t'

comparison between 'int' & 'uint32_t' gives warning. After some compiler
version it is smart enough to not give a warning, but casting is
required for old compilers.

And back to my comment above, casting one of the parameter to
'lcoreid_t' also works, as it forcing promotion to 'unsigned int'
instead. But logically casting looks odd, so keeping casting result.