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

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

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>
> ---
>  lib/librte_eal/common/include/rte_log.h | 12 ++++++++----
>  lib/librte_eal/rte_eal_version.map      |  8 +++++++-
>  2 files changed, 15 insertions(+), 5 deletions(-)
> 
> diff --git a/lib/librte_eal/common/include/rte_log.h b/lib/librte_eal/common/include/rte_log.h
> index cbb4184..c3aff00 100644
> --- a/lib/librte_eal/common/include/rte_log.h
> +++ b/lib/librte_eal/common/include/rte_log.h
> @@ -209,9 +209,6 @@ int rte_log_cur_msg_logtype(void);
>  int rte_log_register(const char *name);
>  
>  /**
> - * @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_log_register() is called inside. If successful, the function tries
> @@ -227,9 +224,16 @@ int rte_log_register(const char *name);
>   *    - >=0: the newly registered log type
>   *    - <0: rte_log_register() error value
>   */
> -__rte_experimental
>  int rte_log_register_type_and_pick_level(const char *name, uint32_t level_def);

+1 to remove experimental from the API.

>  
> +#define RTE_LOG_REGISTER(token, name, level, fallback) \
> +RTE_INIT(token##_init) \

Does it still need to be an init time call?
Since it is dynamic now it can be during probe, even log name can be a paramter
to the "struct rte_driver" and log can be registered automatically during probe,
not sure how complex it becomes.

> +{ \
> +	token = rte_log_register_type_and_pick_level(name, level); \
> +	if (token < 0) \

The failure can be because component can try to register existing log name, or
there is no enough memory, do you think does it worth to do log, or some
additional work if component is trying to register existing log name?

> +		token = fallback; \

Does the 'fallback' needs to be provided by user, it looks like everyone will
just copy/paste 'RTE_LOGTYPE_PMD' for drivers, and does it really needs to be
configurable since it is fallback.

Why not provide a hardcoded type for the failure case? And for that case perhaps
create a more generic logtype, something like "RTE_LOGTYPE_FALLBACK" so that it
can be as it is from all components?