Re: -git tree build failure #2: drivers/net/cnic.c:2520: error: implicit declaration of function ‘__symbol_get’

Mike Christie
2009-06-15T01:28:51Z

James Bottomley wrote:
> On Sat, 2009-06-13 at 17:43 -0700, Michael Chan wrote:
>> On Sat, 2009-06-13 at 13:42 -0700, James Bottomley wrote:
>>> On Sat, 2009-06-13 at 13:11 -0700, Linus Torvalds wrote:
>>>>
>>>> That makes no sense.
>>>>
>>>> Look at the first #include in the file - it already includes
>>>> <linux/module.h>.
>>>>
>>>> Why do we need to do it twice?
>>> We don't ... it's the wrong fix. The actual problem is that
>>> __symbol_get() is only defined for the modular case. What it looks to
>>> be doing is a reflection call on bnx2_cnic_probe(). I'm not sure why
>>> it's doing this ... other than perhaps cnic wants to avoid an explicit
>>> bnx2 dependency? I actually think it's incorrect, since the netdev code
>>> before it just checked bnx2 is present, so I see no harm in an explicit
>>> call, so this should fix it.
>>>
>>> If it had a good reason for the reflective call, then symbol_get()
>>> without the __ should be used.
>>>
>>> Michael Chan, could you confirm?
>>>
>> Thanks James and Ingo. We don't want to have a symbol dependency on
>> bnx2 because this driver eventually will support the 10G bnx2x driver as
>> well. So we want the driver to support either or both NIC drivers
>> without both drivers loaded. Please use the patch below.
>
> Um, but that's not going to work very well. When you have your 10G
> driver, they'll both have to export the symbol name bnx2_cnic_probe
> which the kernel isn't going to like. You can differentiate the symbols
> and add a multiple symbol lookup in init_bnx2_cnic(), but that's getting
> ugly.
>
> What about doing something more standard, like bus matching? That's how
> the SCSI upper layer drivers work: we export a virtual SCSI bus and
> they bind to it if a supporting device appears. You could do something
> similar exporting a virtual cnic bus from your network drivers and get
> the cnic driver to bind to it.
>

Something like bus matching would be nice. I think this is going to be a
bigger problem in the future with everyone putting as many functions on
a card as possible. We already have the cxgb3 net driver with a iwarp
(iw_cxgb3) and iscsi (cxgb3i) driver, so maybe something in the net or
driver model code would be best?

Today, you can't have two pci_drivers attaching to the same device can you?