On 4/7/20 4:35 PM, John Garry wrote:
On 07/04/2020 15:00, Hannes Reinecke wrote:
On 4/7/20 1:54 PM, John Garry wrote:
On 06/04/2020 10:05, Hannes Reinecke wrote:
[ .. ]
This would be okay if 'this_id' would have been defined by the driver;
sadly, most drivers which are affected here do set 'this_id' to -1.
So we wouldn't have a nice target ID to allocate the device from, let
alone the problem that we would have to emulate a complete scsi device
with all required minimal command support etc.
And I'm not quite sure how well that would play with the exising SCSI
host template; the device we'll be allocating would have basically
nothing in common with the 'normal' SCSI devices.
What we could do, though, is to try it the other way round:
Lift the request queue from scsi_get_host_dev() into the scsi host
itself, so that scsi_get_host_dev() can use that queue, but we also
would be able to use it without a SCSI device attached.
wouldn't that limit 1x scsi device per host, not that I know if any
more would ever be required? But it does still seem better to use the
request queue in the scsi device.
My concern is this:
struct scsi_device *scsi_get_host_dev(struct Scsi_Host *shost)
{
[ .. ]
starget = scsi_alloc_target(&shost->shost_gendev, 0,
shost->this_id);
[ .. ]
and we have typically:
drivers/scsi/hisi_sas/hisi_sas_v3_hw.c: .this_id = -1,
It's _very_ uncommon to have a negative number as the SCSI target
device; in fact, it _is_ an unsigned int already.
FWIW, the only other driver (gdth) which I see uses this API has this_id
= -1 in the scsi host template.
But alright, I'll give it a go; let's see what I'll end up with.
note: If we want a fixed scsi_device per host, calling
scsi_mq_setup_tags() -> scsi_get_host_dev() will fail as shost state is
not running. Maybe we need to juggle some things there to provide a
generic solution.
It might even get worse, as during device setup things like
'slave_alloc' etc is getting called, which has a fair chance of getting
confused for non-existing devices.
Cf qla2xxx:qla2xx_slave_alloc() is calling starget_to_rport(), which
will get us a nice oops when accessing a target which is _not_ the child
of a fc remote port.
And this is why I'm not utterly keen on this approach; auditing all
these callbacks is _not_ fun.
Cheers,
Hannes
--
Dr. Hannes Reinecke Teamlead Storage & Networking
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