15/04/2021 14:03, Andrew Rybchenko: > On 4/15/21 2:57 PM, Thomas Monjalon wrote: > > 15/04/2021 10:15, Andrew Rybchenko: > >>> RTE_FUNC_PTR_OR_ERR_RET(*dev->dev_ops->dev_configure, -ENOTSUP); > >> In theory, the first argument is sufficient to make the ops > >> check, but I think it is the right solution to keep it as is > >> since current tendency is to check operation support when > >> driver callback is really required and we're going to use it. > >> However, if we do it just after port_id check, we'll have a > >> way to check for callback support without any side effects > >> if we provide invalid argument value. I.e. if -ENOTSUP is > >> returned, callback is not supported, if -EINVAL, callback is > >> supported (but argument is invalid and nothing done). > >> However, it looks a bit fragile and not always possible. > >> Thoughts on it are welcome. > > Sorry I don't understand it fully. > > You say we should check for ENOTSUP at the very beginning? > > I'm just trying to consider it and understand if it would be > right or wrong.
I think it's better to check things when they are required. If the application does not give the right parameter, it won't be caught until a supporting device will be used. If the appplication gives the wrong parameter on purpose, because it won't be supported, then it's better not calling the function.
