[PATCH] libata-eh-fw: implement ata_port_schedule_eh() and ata_port_abort()

ata_port_schedule_eh() directly schedules EH for @ap without
associated qc.  Once EH scheduled, no further qc is allowed and EH
kicks in as soon as all currently active qc's are drained.

ata_port_abort() schedules all currently active commands for EH by
qc_completing them with ATA_QCFLAG_FAILED set.  If ata_port_abort()
doesn't find any qc to abort, it directly schedule EH using
ata_port_schedule_eh().

These two functions provide ways to invoke EH for conditions which
aren't directly related to any specfic qc.

Signed-off-by: Tejun Heo <htejun@gmail.com>
diff --git a/include/linux/libata.h b/include/linux/libata.h
index 6023f32..086e146 100644
--- a/include/linux/libata.h
+++ b/include/linux/libata.h
@@ -662,6 +662,10 @@
  * EH
  */
 extern void ata_eng_timeout(struct ata_port *ap);
+
+extern void ata_port_schedule_eh(struct ata_port *ap);
+extern int ata_port_abort(struct ata_port *ap);
+
 extern void ata_eh_qc_complete(struct ata_queued_cmd *qc);
 extern void ata_eh_qc_retry(struct ata_queued_cmd *qc);