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Date:   Wed, 6 Jul 2022 15:30:30 -0600
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To:     Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        Christoph Hellwig <hch@lst.de>
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From:   Logan Gunthorpe <logang@deltatee.com>
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Subject: Re: [PATCH v7 20/21] PCI/P2PDMA: Introduce pci_mmap_p2pmem()
Precedence: bulk


On 2022-07-06 01:04, Greg Kroah-Hartman wrote:
> On Wed, Jul 06, 2022 at 08:51:27AM +0200, Christoph Hellwig wrote:
>> 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?
> 
> As you mention, you will have to pass different things down into sysfs
> in order for that to be possible.  If it matches the resource files like
> we currently have today, that might not be that bad, but it still feels
> odd to me.  Let's see an implementation and a Documentation/ABI/ entry
> first though.

I'll work something up in the coming weeks.

Thanks,

Logan