netdev - Re: [PATCH 1/4] net: sgi: ioc3-eth: don't abuse dma_direct

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Message-ID: <20191030223818.GA23807@lst.de>
Date:   Wed, 30 Oct 2019 23:38:18 +0100
From:   Christoph Hellwig <hch@....de>
To:     Thomas Bogendoerfer <tbogendoerfer@...e.de>
Cc:     Christoph Hellwig <hch@....de>,
        "David S. Miller" <davem@...emloft.net>,
        linux-mips@...r.kernel.org, netdev@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/4] net: sgi: ioc3-eth: don't abuse dma_direct_* calls

On Wed, Oct 30, 2019 at 11:05:49PM +0100, Thomas Bogendoerfer wrote:
> On Wed, 30 Oct 2019 14:12:30 -0700
> Christoph Hellwig <hch@....de> wrote:
> 
> > dma_direct_ is a low-level API that must never be used by drivers
> > directly.  Switch to use the proper DMA API instead.
> 
> is the 4kb/16kb alignment still guaranteed ? If not how is the way
> to get such an alignment ?

The DMA API gives you page aligned memory. dma_direct doesn't give you
any gurantees as it is an internal API explicitly documented as not
for driver usage that can change at any time.