Re: [dpdk-dev] Non-argv dependant rte_eal_init() call

[Antti Kantee <pooka@iki.fi>]

On 1.8.2013 19:13, Marc Sune wrote:
> Regarding the rte_eal_init(), if the concern is the number of parameters
> and backwards compatibility, a typical solution is to create a struct
> containing the parameters:
>
> <code>
> typedef struct eal_init_params{
>      uint64_t coremask;
>      unsigned int num_of_cache_lines;
>      /* Add here more parmeters in future versions... */
> }eal_init_params_t;
>
> int rte_eal_init(eal_init_params_t* params);
> </code>
>
> Therefore the user code, is always backwards compatible (provided that
> is properly recompiled).

I don't think that's a good interface because:
1) like you say, you need to recompile everything always to make sure 
the passed struct is of the right size
2) it's less obvious how to pass optional parameters, or more 
accurately, how to not pass them.  You could add some 
eal_init_defaults() interface, but see "3".
3) with every DPDK upgrade you need to evaluate new members of the 
struct to determine their default values.  Mandatory parameters need to 
be addressed either way, but at least the current scheme gives an 
explicit error if you omit one instead of defaulting to some perhaps 
unwanted behavior.

I think the current way of passing of a string tuple vector is fine, 
though I agree it's a little counter-intuitive when you need to invent 
argv[0] in case you're not just passing in argv[] opaquely.  I pass 
"if_dpdk" from my TCP driver, and I haven't lost too much sleep over it.

My only annoyance is that eal_init() takes a non-const.

   - antti