Re: [dpdk-dev] [PATCH 02/11] log: define logtype register wrapper for drivers

[Thomas Monjalon <thomas@monjalon.net>]

05/09/2019 08:29, Andrew Rybchenko:
> On 9/4/19 11:44 PM, Thomas Monjalon wrote:
> > 04/09/2019 21:58, Andrew Rybchenko:
> >> On September 4, 2019 22:42:12 Thomas Monjalon <thomas@monjalon.net> wrote:
> >>
> >>> 04/09/2019 21:21, Andrew Rybchenko:
> >>>> On 9/4/19 8:45 PM, Thomas Monjalon wrote:
> >>>>> 03/09/2019 10:47, Ferruh Yigit:
> >>>>>> On 9/3/2019 9:06 AM, David Marchand wrote:
> >>>>>>> On Mon, Sep 2, 2019 at 4:29 PM Ferruh Yigit <ferruh.yigit@intel.com> wrote:
> >>>>>>>> On 8/19/2019 12:41 PM, David Marchand wrote:
> >>>>>>>>> The function rte_log_register_type_and_pick_level() fills a gap for
> >>>>>>>>> dynamically loaded code (especially drivers) who would not pick up
> >>>>>>>>> the log level passed at startup.
> >>>>>>>>>
> >>>>>>>>>
> >>>>>>>>> Let's promote it to stable and export it for use by drivers via
> >>>>>>>>> a wrapper.
> >>>>>>>>>
> >>>>>>>>>
> >>>>>>>>> Signed-off-by: David Marchand <david.marchand@redhat.com>
> >>>>>>>>> ---
> >>>>> [...]
> >>>>>>>>> /**
> >>>>>>>>> - * @warning
> >>>>>>>>> - * @b EXPERIMENTAL: this API may change without prior notice
> >>>>>>>>> - *
> >>>>>>>>> * Register a dynamic log type and try to pick its level from EAL options
> >>>>> [...]
> >>>>>>>>> -__rte_experimental
> >>>>>>>>> int rte_log_register_type_and_pick_level(const char *name, uint32_t level_def);
> >>>>>>>> +1 to remove experimental from the API.
> >>>>> I am not sure about this function API.
> >>>>> Why we combined register and level setting in one function?
> >>>> See [1]
> >>>>
> >>>> [1] http://git.dpdk.org/dpdk/commit/?id=b22e77c026
> >>> Sorry, it does not explain why we mix both operations in one function.
> >> Exactly to have one function instead of repeating two function calls
> >> everywhere. Log level should be set when log type is registered. Yes, it is
> >> possible to factor out a function just to pick log level, but I'm not sure
> >> it makes sense separately.
> >>
> >> In fact may be it makes sense to substitute just register with this one
> >> (I.e. remove simple register from piblic API and do not highlight that
> >> level is picked up in function name).
> > Given that we use it in a macro, we could keep two separate functions
> > for logtype register and minimum log level (note that "minimum" is
> > currently a missing word in these functions).
> > Anyway, we will always use the single macro in our libraries.
> 
> I don't understand why "minimum" is missing. It assigns level specified
> for the pattern if it matches, or use level_def if no match. No level
> comparison, last match wins. If "minimum" refers to minimum logged
> level, it matches rte_log_set_level() which has no "minimum" as well
> in neither name nor description. Moreover, EMERG is smaller than
> DEBUG and if we treat log levels as numbers, it sets maximum level
> which is logged.

Yes it is maximum.
I mean even in rte_log_set_level() we don't have such word.
It is a detail.

> There are two usages right now without a macro, but it is not that
> important. What I'm trying to say is that rte_log_register() plus setting
> default after register is too error prone. It is the source of the bug
> which we tried to workaround introducing the function.
> 
> If user sets log level (using eal command-line options), no special
> efforts should be required to assign it on register. So, I think register
> should always do it. The function name is not ideal since it is highlights
> details which are not really interesting. It is logging support details that
> log levels may be set before log types registration.
> 
> if we accept DPDK-wide default, it makes level_def parameter
> unnecessary and the functionality to pick level may be simply
> moved to rte_log_register() (using helper internal function) and
> I see no good reasons why we really need type-specific defaults.

I agree it can be merged in rte_log_register().