netdev - Re: use exact allocation for dma coherent memory

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Message-ID: <20190708184351.GA12877@lst.de>
Date:   Mon, 8 Jul 2019 20:43:51 +0200
From:   Christoph Hellwig <hch@....de>
To:     Arend Van Spriel <arend.vanspriel@...adcom.com>
Cc:     Christoph Hellwig <hch@....de>,
        Maarten Lankhorst <maarten.lankhorst@...ux.intel.com>,
        Maxime Ripard <maxime.ripard@...tlin.com>,
        Sean Paul <sean@...rly.run>, David Airlie <airlied@...ux.ie>,
        Daniel Vetter <daniel@...ll.ch>,
        Jani Nikula <jani.nikula@...ux.intel.com>,
        Joonas Lahtinen <joonas.lahtinen@...ux.intel.com>,
        Rodrigo Vivi <rodrigo.vivi@...el.com>,
        Ian Abbott <abbotti@....co.uk>,
        H Hartley Sweeten <hsweeten@...ionengravers.com>,
        devel@...verdev.osuosl.org, linux-s390@...r.kernel.org,
        Intel Linux Wireless <linuxwifi@...el.com>,
        linux-rdma@...r.kernel.org, netdev@...r.kernel.org,
        intel-gfx@...ts.freedesktop.org, linux-wireless@...r.kernel.org,
        linux-kernel@...r.kernel.org, dri-devel@...ts.freedesktop.org,
        linux-mm@...ck.org, iommu@...ts.linux-foundation.org,
        "moderated list:ARM PORT" <linux-arm-kernel@...ts.infradead.org>,
        linux-media@...r.kernel.org
Subject: Re: use exact allocation for dma coherent memory

On Tue, Jul 02, 2019 at 11:48:44AM +0200, Arend Van Spriel wrote:
> You made me look ;-) Actually not touching my drivers so I'm off the hook. 
> However, I was wondering if drivers could know so I decided to look into 
> the DMA-API.txt documentation which currently states:
>
> """
> The flag parameter (dma_alloc_coherent() only) allows the caller to
> specify the ``GFP_`` flags (see kmalloc()) for the allocation (the
> implementation may choose to ignore flags that affect the location of
> the returned memory, like GFP_DMA).
> """
>
> I do expect you are going to change that description as well now that you 
> are going to issue a warning on __GFP_COMP. Maybe include that in patch 
> 15/16 where you introduce that warning.

Yes, that description needs an updated, even without this series.
I'll make sure it is more clear.