linux-kernel - Re: [PATCH 2/3] firewire-sbp2: Ignore SBP-2 targets on the local node

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Message-ID: <4F365C01.6000807@ladisch.de>
Date:	Sat, 11 Feb 2012 13:16:01 +0100
From:	Clemens Ladisch <clemens@...isch.de>
To:	Stefan Richter <stefanr@...6.in-berlin.de>
CC:	Chris Boot <bootc@...tc.net>, Greg KH <gregkh@...uxfoundation.org>,
	linux1394-devel@...ts.sourceforge.net, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 2/3] firewire-sbp2: Ignore SBP-2 targets on the local
 node

Stefan Richter wrote:
> On Feb 10 Chris Boot wrote:
>> The firewire-sbp2 module tries to login to an SBP-2/3 target even when
>> it is running on the local node, which fails because of the inability to
>> fetch data from DMA mapped regions using firewire transactions on the
>> local node.
>
> In the long run, we might want to support target and initiator set up to
> reside on the same node and talking to each other via loopback, if
> somebody really needs it and if it can be done with reasonably little
> effort.

Handling SBP data packets in the driver is required if we do not want to
allow remote DMA from any device that claims to be a target.  This is
somewhere on my todo list.

>> +	/* ignore targets on the local node */
>> +	if (device->node == device->card->local_node) {
>> +		dev_set_drvdata(&unit->device, NULL);
>> +		return 0;
>> +	}
>
> But I do wonder:  Shouldn't this be implemented by returning from the
> driver probe method with an error?

AFAIK zero means "attach", and the drvdata pointer has no meaning to the
core.

> If so, which errno should be returned?

-ENODEV or -ENXIO.


Regards,
Clemens
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