[openib-general] [PATCH] netdevice.h: Add RDMA private pointer to the net_device structure

[Sean Hefty]

Hal Rosenstock wrote:
>>I'm trying to understand who would use this field and what it would contain. 
>> From discussions so far, it looks like only an IP to IB address translation 
>>mechanism would need it.  And the only value that's required seems to be the 
>>pkey.  Other values could be returned as well to possibly simplify things, but 
>>not sure that anything else is required.
> 
> Also, ib_device and port as well as PKey.

The device and port can be retrieved by looking up the GID in a local device 
list, though it's a little inefficient.  I agree that these 3 values are ideal, 
but not sure that having them helps.  (And returning the device pointer could 
actually lead to misuse.)

What's still not clear to me is how an ib_device pointer would be used with 
respect to device removal.  Ultimately a client needs to get a pointer to an 
ib_device that they can use for QP allocation, etc.  I think that we need to 
examine the problem from a ULP's perspective, versus going up a single layer in 
the stack.

For example, currently the CMA queries an address translation service to convert 
an IP address into a GID.  The CMA searches its device list until it finds a 
match on the GID.  This permits synchronization with device removal.

Given the current device registration interface, it seems that a search through 
a device list is needed at some point.  The only alternative that I can think of 
is to make use of a more complex reference counting scheme.

- Sean