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

[David Marchand <david.marchand@redhat.com>]

On Thu, Sep 5, 2019 at 8:29 AM Andrew Rybchenko
<arybchenko@solarflare.com> wrote:
>
> 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.
>
> 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.

Well this would require to touch quite some components that are not
aligned, but I can't disagree with you :-).
I'll prepare a v2 and identify which drivers are not ready for this.

I also have some additional changes in mind.
This should prevent the log register from failing (and no need for the
"fallback" stuff then).


-- 
David Marchand