[PATCH v3 1/5] kvargs: add one new process API

[fengchengwen]

Hi Ferruh,

On 2023/11/3 21:09, Ferruh Yigit wrote:
> On 11/3/2023 7:38 AM, Chengwen Feng wrote:
>> The rte_kvargs_process() was used to parse key-value (e.g. socket_id=0),
>> it also supports to parse only-key (e.g. socket_id). But many drivers's
>> callback can only handle key-value, it will segment fault if handles
>> only-key. so the patchset [1] was introduced.
>>
>> Because the patchset [1] modified too much drivers, therefore:
>> 1) A new API rte_kvargs_process_opt() was introduced, it inherits the
>> function of rte_kvargs_process() which could parse both key-value and
>> only-key.
>> 2) Constraint the rte_kvargs_process() can only parse key-value.
>>
> 
> Hi Chengwen,
> 
> This works, but behavior change in 'rte_kvargs_process()' can hit some
> exiting users who handles both "key=value" and "key" cases.
> 
> Other option is to keep 'rte_kvargs_process()' behavior same but add a
> new API like 'rte_kvargs_process_safe()' that checks "value == NULL"
> case, but this requires more existing code to change and in this option
> existing users doesn't get the benefit of the NULL check by default.
> 
> 
> Assuming number of the users that use 'rte_kvargs_process()' for
> "key=value" is majority, OK to continue with your change, but please
> document this in the release notes to highlight.

Thanks, already fix in v4

> 
> 
> 
>> [1] https://patches.dpdk.org/project/dpdk/patch/20230320092110.37295-1-fengchengwen@huawei.com/
>>
>> Signed-off-by: Chengwen Feng <fengchengwen at huawei.com>
>> ---
>>  lib/kvargs/rte_kvargs.c | 29 ++++++++++++++++++++++++++++-
>>  lib/kvargs/rte_kvargs.h | 28 ++++++++++++++++++++++++++++
>>  lib/kvargs/version.map  |  3 +++
>>  3 files changed, 59 insertions(+), 1 deletion(-)
>>
>> diff --git a/lib/kvargs/rte_kvargs.c b/lib/kvargs/rte_kvargs.c
>> index c77bb82feb..5ce8664238 100644
>> --- a/lib/kvargs/rte_kvargs.c
>> +++ b/lib/kvargs/rte_kvargs.c
>> @@ -168,7 +168,7 @@ rte_kvargs_count(const struct rte_kvargs *kvlist, const char *key_match)
>>  }
>>  
>>  /*
>> - * For each matching key, call the given handler function.
>> + * For each matching key in key/value, call the given handler function.
>>   */
>>  int
>>  rte_kvargs_process(const struct rte_kvargs *kvlist,
>> @@ -179,6 +179,33 @@ rte_kvargs_process(const struct rte_kvargs *kvlist,
>>  	const struct rte_kvargs_pair *pair;
>>  	unsigned i;
>>  
>> +	if (kvlist == NULL)
>> +		return 0;
>> +
> 
> I think it should return error here, ignoring arg silently with success
> can cause trouble in the application. If error returned, at least
> application can know argument not provided as it should be (value is
> missing).

fix in v4.

> 
> 
>> +	for (i = 0; i < kvlist->count; i++) {
>> +		pair = &kvlist->pairs[i];
>> +		if (pair->value == NULL)
>> +			continue;
>> +		if (key_match == NULL || strcmp(pair->key, key_match) == 0) {
>> +			if ((*handler)(pair->key, pair->value, opaque_arg) < 0)
>> +				return -1;
>> +		}
>> +	}
>> +	return 0;
>> +}
>> +
> 
> 'rte_kvargs_process()' & 'rte_kvargs_process_opt()' implementations are
> very similar, to reduce duplication what about create
> 'rte_kvargs_process_common()' static function and both use this common
> with different parameter?

nice catch, fix in v4.

> 
> 
>> +/*
>> + * For each matching key in key/value or only-key, call the given handler function.
>> + */
>> +int
>> +rte_kvargs_process_opt(const struct rte_kvargs *kvlist,
>> +		       const char *key_match,
>> +		       arg_handler_t handler,
>> +		       void *opaque_arg)
>> +{
>> +	const struct rte_kvargs_pair *pair;
>> +	unsigned int i;
>> +
>>  	if (kvlist == NULL)
>>  		return 0;
>>  
>> diff --git a/lib/kvargs/rte_kvargs.h b/lib/kvargs/rte_kvargs.h
>> index 4900b750bc..522e83f757 100644
>> --- a/lib/kvargs/rte_kvargs.h
>> +++ b/lib/kvargs/rte_kvargs.h
>> @@ -195,6 +195,34 @@ const char *rte_kvargs_get_with_value(const struct rte_kvargs *kvlist,
>>  int rte_kvargs_process(const struct rte_kvargs *kvlist,
>>  	const char *key_match, arg_handler_t handler, void *opaque_arg);
>>  
>> +/**
>> + * @warning
>> + * @b EXPERIMENTAL: this API may change without prior notice.
>> + *
>> + * Call a handler function for each key/value or only-key matching the key
>> + *
>>
> 
> In API documentation, the difference between  'rte_kvargs_process_opt()'
> & 'rte_kvargs_process()' is, 'rte_kvargs_process()' doesn't have "or
> only-key", this is easy to miss.
> Can you please add more not to 'rte_kvargs_process()' saying on
> "only-key" case it returns error?

add one @note in v4.

> 
> 
>> + * For each key/value or only-key association that matches the given key, calls
>> + * the handler function with the for a given arg_name passing the value on the
>> + * dictionary for that key and a given extra argument.
>> + *
>> + * @param kvlist
>> + *   The rte_kvargs structure. No error if NULL.
>> + * @param key_match
>> + *   The key on which the handler should be called, or NULL to process handler
>> + *   on all associations
>> + * @param handler
>> + *   The function to call for each matching key
>> + * @param opaque_arg
>> + *   A pointer passed unchanged to the handler
>> + *
>> + * @return
>> + *   - 0 on success
>> + *   - Negative on error
>> + */
>> +__rte_experimental
>> +int rte_kvargs_process_opt(const struct rte_kvargs *kvlist,
>> +	const char *key_match, arg_handler_t handler, void *opaque_arg);
>> +
>>
> 
> I am not sure about the API name, 'rte_kvargs_process_opt()', what is
> 'opt' here, "optional"?

Yes, it mean optional of value is valid or NULL.

> What about 'rte_kvargs_process_unsafe()', not quite strong on this too
> but not able to come with better one, please feel free to try other
> alternatives.

also have no better name, so keep the same with v3.

Thanks
Chengwen

> 
> 
>>  /**
>>   * Count the number of associations matching the given key
>>   *
>> diff --git a/lib/kvargs/version.map b/lib/kvargs/version.map
>> index 387a94e725..15d482e9b3 100644
>> --- a/lib/kvargs/version.map
>> +++ b/lib/kvargs/version.map
>> @@ -16,4 +16,7 @@ EXPERIMENTAL {
>>  
>>  	# added in 21.11
>>  	rte_kvargs_get_with_value;
>> +
>> +	# added in 23.11
>> +	rte_kvargs_process_opt;
>>  };
> 
> .
>