Return-path: Received: from s3.sipsolutions.net ([5.9.151.49]:56171 "EHLO sipsolutions.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932348AbbLNNax (ORCPT ); Mon, 14 Dec 2015 08:30:53 -0500 Message-ID: <1450099851.3871.19.camel@sipsolutions.net> (sfid-20151214_143057_194535_10599F21) Subject: Re: SUPPORTS_CLONED_SKBS question From: Johannes Berg To: Janusz Dziedzic , linux-wireless@vger.kernel.org, Felix Fietkau , Ido Yariv Date: Mon, 14 Dec 2015 14:30:51 +0100 In-Reply-To: (sfid-20151214_135825_770699_738420CE) References: (sfid-20151214_135825_770699_738420CE) Content-Type: text/plain; charset="UTF-8" Mime-Version: 1.0 Sender: linux-wireless-owner@vger.kernel.org List-ID: +Ido. On Mon, 2015-12-14 at 13:58 +0100, Janusz Dziedzic wrote: > Base of SUPPORTS_CLONED_SKBS description, we can set this flag > in case driver will not touch payload or tailroom. > What exactly does it mean? Well, you must not modify the data in a way that would make the clone invalid. That means you can't write to any of the data, essentially. > What in case of headroom, while ath9k already move 80211 header - add > padding > after header (skb_push(hdrlen & 3) + memmove) and remove this padding > in tx_completion. I think that should be OK since you don't touch the payload data or the tailroom. > What in case of FCS? What about it? Hopefully that's added by hardware and has no effect on the skb?! johannes