linux-kernel - Re: [PATCH v2] dma-contiguous: define proper name for global cma region

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Message-ID: <20230802094725.GA28241@lst.de>
Date:   Wed, 2 Aug 2023 11:47:25 +0200
From:   Christoph Hellwig <hch@....de>
To:     John Stultz <jstultz@...gle.com>
Cc:     Christoph Hellwig <hch@....de>,
        Pintu Agarwal <pintu.ping@...il.com>,
        Pintu Kumar <quic_pintu@...cinc.com>,
        linux-kernel@...r.kernel.org, akpm@...ux-foundation.org,
        linux-mm@...ck.org, m.szyprowski@...sung.com, robin.murphy@....com,
        iommu@...ts.linux.dev, Sumit Semwal <sumit.semwal@...aro.org>,
        Benjamin Gaignard <benjamin.gaignard@...labora.com>,
        Liam Mark <lmark@...eaurora.org>,
        Laura Abbott <labbott@...hat.com>,
        Brian Starkey <Brian.Starkey@....com>,
        Christian König <christian.koenig@....com>,
        linux-media@...r.kernel.org, dri-devel@...ts.freedesktop.org,
        linaro-mm-sig@...ts.linaro.org
Subject: Re: [PATCH v2] dma-contiguous: define proper name for global cma
 region

On Tue, Aug 01, 2023 at 10:39:04PM -0700, John Stultz wrote:
> So, forgive me, I've not had a chance to look into this, but my
> recollection was "reserved" is the name we see on x86, but other names
> are possibly provided via the dts node?

Indeed, dma_contiguous_default_area can also be set through
rmem_cma_setup, which then takes the name from DT.

> I believe on the hikey board its "linux,cma" is the name, so forcing
> it to reserved would break that.
> 
> Maybe instead add a compat config option to force the cma name (so x86
> can set it to "default" if needed)?


I think we'll just need to leave it as-is.  I with dma-heaps had never
exposed the name to userspace, but we'll have to lіve with it now.