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

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Message-Id: <20191031095430.148daca03517c00f3e2b32ff@suse.de>
Date:   Thu, 31 Oct 2019 09:54:30 +0100
From:   Thomas Bogendoerfer <tbogendoerfer@...e.de>
To:     Christoph Hellwig <hch@....de>
Cc:     "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, 30 Oct 2019 23:38:18 +0100
Christoph Hellwig <hch@....de> wrote:

> 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.

I didn't want to argue about that. What I'm interested in is a way how 
to allocate dma memory, which is 16kB aligned, via the DMA API ?

Thomas.

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