Re: [PATCH 0/7] IB/hfi1: Remove write() and use ioctl() for user access

[Dennis Dalessandro <dennis.dalessandro-ral2JQCrhuEAvxtiuMwx3w@public.gmane.org>]

On Mon, Apr 18, 2016 at 12:24:53PM -0600, Jason Gunthorpe wrote:
>On Mon, Apr 18, 2016 at 02:15:36PM -0400, Dennis Dalessandro wrote:
>
>> Point taken on eprom cdev. We should be able to simply drop the last two
>> patches of this series.
>
>I would like to hear more explanation about this snoop thing, and
>where it lives in the driver today. That also seems inappropriate.
>

Fair enough. I will say the name "snoop" may not be the best and perhaps
adds to the confusion. Basically it's a diagnostic interface that lets
user space do things without involving the rest of the kernel (verbs, MAD,
etc). It can bring the port up and down, set link credits, and get the
status for instance.

Then there are the things it can do with packets. It can send packets
generated by user space. So we can craft all sorts of packets that would not
otherwise be able to be sent through verbs. It also captures packets and
supports basic filtering and hands them to user space before the packets
ever make it to the verbs layer. Depending on mode, packets may be dropped 
or passed on to verbs.

We've always just considered this hfi diagnostic stuff. Is there interest in 
this sort of functionality on a more broad level?

-Denny
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