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Date:   Wed, 6 Jul 2022 08:51:27 +0200
From:   Christoph Hellwig <hch@lst.de>
To:     Logan Gunthorpe <logang@deltatee.com>
Cc:     Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        Christoph Hellwig <hch@lst.de>, Jason Gunthorpe <jgg@ziepe.ca>,
        linux-kernel@vger.kernel.org, linux-nvme@lists.infradead.org,
        linux-block@vger.kernel.org, linux-pci@vger.kernel.org,
        linux-mm@kvack.org, iommu@lists.linux-foundation.org,
        Stephen Bates <sbates@raithlin.com>,
        Dan Williams <dan.j.williams@intel.com>,
        Christian =?iso-8859-1?Q?K=F6nig?= <christian.koenig@amd.com>,
        John Hubbard <jhubbard@nvidia.com>,
        Don Dutile <ddutile@redhat.com>,
        Matthew Wilcox <willy@infradead.org>,
        Daniel Vetter <daniel.vetter@ffwll.ch>,
        Minturn Dave B <dave.b.minturn@intel.com>,
        Jason Ekstrand <jason@jlekstrand.net>,
        Dave Hansen <dave.hansen@linux.intel.com>,
        Xiong Jianxin <jianxin.xiong@intel.com>,
        Bjorn Helgaas <helgaas@kernel.org>,
        Ira Weiny <ira.weiny@intel.com>,
        Robin Murphy <robin.murphy@arm.com>,
        Martin Oliveira <martin.oliveira@eideticom.com>,
        Chaitanya Kulkarni <ckulkarnilinux@gmail.com>,
        Ralph Campbell <rcampbell@nvidia.com>,
        Bjorn Helgaas <bhelgaas@google.com>
Subject: Re: [PATCH v7 20/21] PCI/P2PDMA: Introduce pci_mmap_p2pmem()
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On Tue, Jul 05, 2022 at 12:16:45PM -0600, Logan Gunthorpe wrote:
> The current version does it through a char device, but that requires
> creating a simple_fs and anon_inode for teardown on driver removal, plus
> a bunch of hooks through the driver that exposes it (NVMe, in this case)
> to set this all up.
> 
> Christoph is suggesting a sysfs interface which could potentially avoid
> the anon_inode and all of the extra hooks. It has some significant
> benefits and maybe some small downsides, but I wouldn't describe it as
> horrid.

Yeah, I don't think is is horrible, it fits in with the resource files
for the BARs, and solves a lot of problems.  Greg, can you explain
what would be so bad about it?