linux-kernel - Re: [PATCH] mm: export cma alloc and release

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Message-ID: <20191003085528.GB21629@arrakis.emea.arm.com>
Date:   Thu, 3 Oct 2019 09:55:28 +0100
From:   Catalin Marinas <catalin.marinas@....com>
To:     Mark Salyzyn <salyzyn@...roid.com>
Cc:     linux-kernel@...r.kernel.org, kernel-team@...roid.com,
        Andrew Morton <akpm@...ux-foundation.org>,
        Yue Hu <huyue2@...ong.com>, Mike Rapoport <rppt@...ux.ibm.com>,
        Will Deacon <will@...nel.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ryohei Suzuki <ryh.szk.cmnty@...il.com>,
        Doug Berger <opendmb@...il.com>,
        Andrey Konovalov <andreyknvl@...gle.com>,
        Peng Fan <peng.fan@....com>, linux-mm@...ck.org,
        Christoph Hellwig <hch@....de>,
        Robin Murphy <robin.murphy@....com>
Subject: Re: [PATCH] mm: export cma alloc and release

On Wed, Oct 02, 2019 at 02:22:48PM -0700, Mark Salyzyn wrote:
> Some drivers can not be turned into a module without cma_alloc and
> cma_release exported.  Examples include ion, and we also found some
> out of tree infiniband and camera drivers.
> 
> Signed-off-by: Mark Salyzyn <salyzyn@...roid.com>
> Cc: kernel-team@...roid.com
> Cc: linux-kernel@...r.kernel.org
> ---
>  mm/cma.c | 2 ++
>  1 file changed, 2 insertions(+)
> 
> diff --git a/mm/cma.c b/mm/cma.c
> index 7fe0b8356775..65d830eea3b1 100644
> --- a/mm/cma.c
> +++ b/mm/cma.c
> @@ -500,6 +500,7 @@ struct page *cma_alloc(struct cma *cma, size_t count, unsigned int align,
>  	pr_debug("%s(): returned %p\n", __func__, page);
>  	return page;
>  }
> +EXPORT_SYMBOL_GPL(cma_alloc);
>  
>  /**
>   * cma_release() - release allocated pages
> @@ -533,6 +534,7 @@ bool cma_release(struct cma *cma, const struct page *pages, unsigned int count)
>  
>  	return true;
>  }
> +EXPORT_SYMBOL_GPL(cma_release);

Aren't drivers supposed to use the DMA API for such allocations rather
than invoking cma_*() directly?

-- 
Catalin