[dpdk-dev] [PATCH 1/7] ethdev: remove unused flag from header

[Vlad Zolotarov]

On 12/04/2017 12:54 PM, Ferruh Yigit wrote:
> On 12/1/2017 6:22 PM, Vlad Zolotarov wrote:
>>
>> On 12/01/2017 06:51 PM, Ferruh Yigit wrote:
>>> On 12/1/2017 2:17 PM, Vlad Zolotarov wrote:
>>>> On 11/30/2017 09:29 PM, Ferruh Yigit wrote:
>>>>> remove RTE_ETHDEV_HAS_LRO_SUPPORT flag from header.
>>>>>
>>>>> Flag seems added with the patch that adds LRO support, and intention
>>>>> looks like giving a pointer to application that library supports LRO.
>>>> Exactly. Removing this flag may make the existing application "think" that LRO
>>>> is not supported.
>>>> Why do you want to remove it to begin with?
>>> I agree that this is a little controversial, and I don't have a strong opinion
>>> about it, I thought twice before sending or not sending the patch :)
>>>
>>> This flag can be useful for the applications that use different versions of the
>>> DPDK library (with the ones does and doesn't support LRO), so that application
>>> can be more portable.
>>> I would understand a dynamic approach, which would be useful for distributed
>>> applications that you don't know and can't control what version of the DPDK
>>> library used.
>>> But here to benefit from this flag you need to compile your application against
>>> DPDK library, and if you are compiling it you already know if your DPDK supports
>>> LRO or not. And this is not something keeps changing platform to platform etc,
>>> after a specific release LRO is always supported.
>> True but DPDK is usually not a part of your source tree - it (should) come as a
>> library and currently there isn't any proper way to query feature set.
>> This flag was also added after a lot of consideration as a rather ugly
>> compromise since there wasn't (and there isn't) a proper way to do that at that
>> (this) time. See more on that below.
>>
>>> And this is the only capability support flag in the ethdev, there are many new
>>> features introduced in each release but they are not advertised by a capability
>>> flag. Only having LRO flag can be confusing.
>>>
>>> _Perhaps_ DPDK should have a way to expose the supported features, and a dynamic
>>> runtime way can be better option than compile time macros, but it should be
>>> generic nothing specific to LRO support.
>> IMO it's not "perhaps" it's a "must" _however_
> This is even wider than ethdev, more like in DPDK scope, we need someone to
> attack this issue.

absolutely!

>
>> you can't remove this flag without giving some other tool to do the same.
> Fair enough, I will drop the patch.
>
>> Querying a DPDK version would be a wrong direction because some Linux
>> distributions (yes, I'm talking about you, Ubuntu) tend to have it's own trees
>> with their own backports and these trees may be light years ahead in their patch
>> level compared to vanilla trees with the same version.
> +1 to have better way than version check.
>
>>>>> Fixes: 8eecb3295aed ("ixgbe: add LRO support")
>>>>> Cc: vladz at cloudius-systems.com
>>>>>
>>>>> Signed-off-by: Ferruh Yigit <ferruh.yigit at intel.com>
>>>>> ---
>>>>>   lib/librte_ether/rte_ethdev.h | 3 ---
>>>>>   1 file changed, 3 deletions(-)
>>>>>
>>>>> diff --git a/lib/librte_ether/rte_ethdev.h b/lib/librte_ether/rte_ethdev.h
>>>>> index 341c2d624..e620c3706 100644
>>>>> --- a/lib/librte_ether/rte_ethdev.h
>>>>> +++ b/lib/librte_ether/rte_ethdev.h
>>>>> @@ -172,9 +172,6 @@ extern "C" {
>>>>>   
>>>>>   #include <stdint.h>
>>>>>   
>>>>> -/* Use this macro to check if LRO API is supported */
>>>>> -#define RTE_ETHDEV_HAS_LRO_SUPPORT
>>>>> -
>>>>>   #include <rte_log.h>
>>>>>   #include <rte_interrupts.h>
>>>>>   #include <rte_dev.h>