linux-kernel - Re: [PATCH 03/22] mm: remove hmm_devmem_add

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Message-ID: <20190614061946.GE7246@lst.de>
Date:   Fri, 14 Jun 2019 08:19:46 +0200
From:   Christoph Hellwig <hch@....de>
To:     Jason Gunthorpe <jgg@...lanox.com>
Cc:     Christoph Hellwig <hch@....de>,
        Dan Williams <dan.j.williams@...el.com>,
        Jérôme Glisse <jglisse@...hat.com>,
        Ben Skeggs <bskeggs@...hat.com>,
        "linux-mm@...ck.org" <linux-mm@...ck.org>,
        "nouveau@...ts.freedesktop.org" <nouveau@...ts.freedesktop.org>,
        "dri-devel@...ts.freedesktop.org" <dri-devel@...ts.freedesktop.org>,
        "linux-nvdimm@...ts.01.org" <linux-nvdimm@...ts.01.org>,
        "linux-pci@...r.kernel.org" <linux-pci@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 03/22] mm: remove hmm_devmem_add_resource

On Thu, Jun 13, 2019 at 06:52:44PM +0000, Jason Gunthorpe wrote:
> On Thu, Jun 13, 2019 at 11:43:06AM +0200, Christoph Hellwig wrote:
> > This function has never been used since it was first added to the kernel
> > more than a year and a half ago, and if we ever grow a consumer of the
> > MEMORY_DEVICE_PUBLIC infrastructure it can easily use devm_memremap_pages
> > directly now that we've simplified the API for it.
> 
> nit: Have we simplified the interface for devm_memremap_pages() at
> this point, or are you talking about later patches in this series.

After this series.  I've just droped that part of the sentence to
avoid confusion.

> I checked this and all the called functions are exported symbols, so
> there is no blocker for a future driver to call devm_memremap_pages(),
> maybe even with all this boiler plate, in future.
> 
> If we eventually get many users that need some simplified registration
> then we should add a devm_memremap_pages_simplified() interface and
> factor out that code when we can see the pattern.

After this series devm_memremap_pages already is simpler to use than
hmm_device_add_resource was before, so I'm not worried at all.  The
series actually net removes lines from noveau (if only a few).