libata-pmp-prep: implement qc_defer helpers

Implement ap->nr_active_links (the number of links with active qcs),
ap->excl_link (pointer to link which can be used by ->qc_defer and is
cleared when a qc with ATA_QCFLAG_CLEAR_EXCL completes), and
ata_link_active().

These can be used by ->qc_defer() to implement proper command
exclusion.  This set of helpers seem enough for both sil24 (ATAPI
exclusion needed) and cmd-switching PMP.

Signed-off-by: Tejun Heo <htejun@gmail.com>
Signed-off-by: Jeff Garzik <jeff@garzik.org>

1 files changed, 8 insertions, 0 deletions

diff --git a/include/linux/libata.h b/include/linux/libata.h
index b0d4ca0d27b4..f9f81fd93293 100644
--- a/include/linux/libata.h
+++ b/include/linux/libata.h
@@ -216,6 +216,7 @@ enum {
         ATA_QCFLAG_DMAMAP       = ATA_QCFLAG_SG | ATA_QCFLAG_SINGLE,
         ATA_QCFLAG_IO           = (1 << 3), /* standard IO command */
         ATA_QCFLAG_RESULT_TF    = (1 << 4), /* result TF requested */
+        ATA_QCFLAG_CLEAR_EXCL   = (1 << 5), /* clear excl_link on completion */
 
         ATA_QCFLAG_FAILED       = (1 << 16), /* cmd failed and is owned by EH */
         ATA_QCFLAG_SENSE_VALID  = (1 << 17), /* sense data valid */
@@ -579,11 +580,13 @@ struct ata_port {
         struct ata_queued_cmd   qcmd[ATA_MAX_QUEUE];
         unsigned long           qc_allocated;
         unsigned int            qc_active;
+        int                     nr_active_links; /* #links with active qcs */
 
         struct ata_link         link;   /* host default link */
 
         int                     nr_pmp_links;   /* nr of available PMP links */
         struct ata_link         *pmp_link;      /* array of PMP links */
+        struct ata_link         *excl_link;     /* for PMP qc exclusion */
 
         struct ata_port_stats   stats;
         struct ata_host         *host;
@@ -1104,6 +1107,11 @@ static inline int ata_link_max_devices(const struct ata_link *link)
         return 1;
 }
 
+static inline int ata_link_active(struct ata_link *link)
+{
+        return ata_tag_valid(link->active_tag) || link->sactive;
+}
+
 static inline struct ata_link *ata_port_first_link(struct ata_port *ap)
 {
         if (ap->nr_pmp_links)