scsi: add support for multiple hardware queues

Allow a SCSI LLD to declare how many hardware queues it supports
by setting Scsi_Host.nr_hw_queues before calling scsi_add_host().

Signed-off-by: Bart Van Assche <bvanassche@acm.org>
Reviewed-by: Sagi Grimberg <sagig@mellanox.com>
Reviewed-by: Martin K. Petersen <martin.petersen@oracle.com>
Signed-off-by: Christoph Hellwig <hch@lst.de>

1 files changed, 8 insertions, 0 deletions

diff --git a/include/scsi/scsi_host.h b/include/scsi/scsi_host.h
index 5e362489ee88..bb9e27815be5 100644
--- a/include/scsi/scsi_host.h
+++ b/include/scsi/scsi_host.h
@@ -638,6 +638,14 @@ struct Scsi_Host {
         short unsigned int sg_prot_tablesize;
         unsigned int max_sectors;
         unsigned long dma_boundary;
+        /*
+         * In scsi-mq mode, the number of hardware queues supported by the LLD.
+         *
+         * Note: it is assumed that each hardware queue has a queue depth of
+         * can_queue. In other words, the total queue depth per host
+         * is nr_hw_queues * can_queue.
+         */
+        unsigned nr_hw_queues;
         /* 
          * Used to assign serial numbers to the cmds.
          * Protected by the host lock.