linux-kernel - Re: [PATCH] mwifiex: set needed_headroom, not hard_header

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Message-Id: <20200312134210.1FC1DC433BA@smtp.codeaurora.org>
Date:   Thu, 12 Mar 2020 13:42:10 +0000 (UTC)
From:   Kalle Valo <kvalo@...eaurora.org>
To:     Brian Norris <briannorris@...omium.org>
Cc:     linux-wireless@...r.kernel.org, <linux-kernel@...r.kernel.org>,
        Ganapathi Bhat <ganapathi.bhat@....com>,
        Nishant Sarmukadam <nishants@...vell.com>,
        Amitkumar Karwar <amitkarwar@...il.com>,
        Xinming Hu <huxinming820@...il.com>,
        Arend Van Spriel <arend@...adcom.com>,
        Brian Norris <briannorris@...omium.org>
Subject: Re: [PATCH] mwifiex: set needed_headroom, not hard_header_len

Brian Norris <briannorris@...omium.org> wrote:

> hard_header_len provides limitations for things like AF_PACKET, such
> that we don't allow transmitting packets smaller than this.
> 
> needed_headroom provides a suggested minimum headroom for SKBs, so that
> we can trivally add our headers to the front.
> 
> The latter is the correct field to use in this case, while the former
> mostly just prevents sending small AF_PACKET frames.
> 
> In any case, mwifiex already does its own bounce buffering [1] if we
> don't have enough headroom, so hints (not hard limits) are all that are
> needed.
> 
> This is the essentially the same bug (and fix) that brcmfmac had, fixed
> in commit cb39288fd6bb ("brcmfmac: use ndev->needed_headroom to reserve
> additional header space").
> 
> [1] mwifiex_hard_start_xmit():
> 	if (skb_headroom(skb) < MWIFIEX_MIN_DATA_HEADER_LEN) {
> 	[...]
> 		/* Insufficient skb headroom - allocate a new skb */
> 
> Fixes: 5e6e3a92b9a4 ("wireless: mwifiex: initial commit for Marvell mwifiex driver")
> Signed-off-by: Brian Norris <briannorris@...omium.org>
> Acked-by: Ganapathi Bhat <ganapathi.gbhat@....com>

Patch applied to wireless-drivers-next.git, thanks.

9454f7a895b8 mwifiex: set needed_headroom, not hard_header_len

-- 
https://patchwork.kernel.org/patch/11407493/

https://wireless.wiki.kernel.org/en/developers/documentation/submittingpatches