From mboxrd@z Thu Jan 1 00:00:00 1970 From: Thomas Monjalon Subject: Re: [PATCH v2 2/2] ethdev: add new offload flag to keep CRC Date: Thu, 29 Mar 2018 09:43:12 +0200 Message-ID: <15555561.lU3UqzoiBB@xps> References: <20180320112631.107105-1-ferruh.yigit@intel.com> <20180321194730.52068-2-ferruh.yigit@intel.com> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7Bit Cc: Ferruh Yigit , Neil Horman , John McNamara , Marko Kovacevic , "dev@dpdk.org" To: Shahaf Shuler Return-path: Received: from out5-smtp.messagingengine.com (out5-smtp.messagingengine.com [66.111.4.29]) by dpdk.org (Postfix) with ESMTP id 1B268271 for ; Thu, 29 Mar 2018 09:43:36 +0200 (CEST) In-Reply-To: List-Id: DPDK patches and discussions List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: dev-bounces@dpdk.org Sender: "dev" 29/03/2018 07:38, Shahaf Shuler: > Wednesday, March 21, 2018 9:48 PM, Ferruh Yigit: > > DEV_RX_OFFLOAD_KEEP_CRC offload flag added. > > > > DEV_RX_OFFLOAD_CRC_STRIP flag will remain one more release but default > > behavior in PMDs is to strip the CRC independent from this flag. > > > > Until DEV_RX_OFFLOAD_CRC_STRIP flag is removed: > > - Setting both KEEP_CRC & CRC_STRIP is INVALID > > - Setting only CRC_STRIP PMD should strip the CRC > > - Setting only KEEP_CRC PMD should keep the CRC > > - Not setting both PMD should strip the CRC > > We cannot have such default behavior, it may break existing applications. > > The API of ethdev offloads says (even though it is not well documented) : DEV_RX_OFFLOAD_CRC_STRIP (emphasis the STRIP). > meaning, if set -> STRIP, if not set -> don't strip. I am aware to at least one application which wants to have the CRC, and for that purpose it naturally don't set the offload flag. > > The fact some PMDs lack the ability to toggle the CRC stripping should be exposed in the "limitations" section of their related guide. > > Up to here, this is the behavior as defined by the API. > > Now, we want to change it, and I think it makes sense. However I think we should take similar approach to what we did with the ethdev offloads API: > 1. at first stage a new offload flag is exposed DEV_RX_OFFLOAD_KEEP_CRC and implemented on the PMDs. This is what is proposed above, except that we change the default behaviour. If we introduce a new flag which is the contrary of the old one, we need to choose which one is the default, so which one has no effect. > 2. there is a conversion function on ethdev. Which for example converts ~DEV_RX_OFFLOAD_CRC_STRIP -> DEV_RX_OFFLOAD_KEEP_CRC for the PMDs. > 3. deprecation of DEV_RX_OFFLOAD_CRC_STRIP for applications and remove of the conversion functions.