linux-kernel - Re: [PATCH 5/5] mm, hmm: mark hmm_devmem_{add, add_resource} EXPORT_SYMBOL

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Date:   Tue, 22 May 2018 14:31:21 -0700
From:   Andrew Morton <akpm@...ux-foundation.org>
To:     Christoph Hellwig <hch@....de>
Cc:     Dan Williams <dan.j.williams@...el.com>,
        Jérôme Glisse <jglisse@...hat.com>,
        Logan Gunthorpe <logang@...tatee.com>, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH 5/5] mm, hmm: mark hmm_devmem_{add, add_resource}
 EXPORT_SYMBOL_GPL

On Tue, 22 May 2018 08:32:36 +0200 Christoph Hellwig <hch@....de> wrote:

> On Mon, May 21, 2018 at 03:35:40PM -0700, Dan Williams wrote:
> > The routines hmm_devmem_add(), and hmm_devmem_add_resource() are small
> > wrappers around devm_memremap_pages(). The devm_memremap_pages()
> > interface is a subset of the hmm functionality which has more and deeper
> > ties into the kernel memory management implementation. It was an
> > oversight that these symbols were not marked EXPORT_SYMBOL_GPL from the
> > outset due to how they originally copied (and now reuse)
> > devm_memremap_pages().
> 
> If we end up keeping this code: absolutely.  Then again I think without
> an actual user this should have never been merged, and should be removed
> until one shows up.
> 

It wasn't simple.  Quite a lot of manufacturers were (are?) developing
quite complex driver code which utilizes hmm.  Merging hmm to give a
stable target for that development and in the expectation that those
things would be coming along was a risk and I don't think we yet know
the outcome.

Jerome, are you able to provide any updates on all of this?