[PATCH] libata: implement dummy port

Implement dummy port which can be requested by setting appropriate bit
in probe_ent->dummy_port_mask.  The dummy port is used as placeholder
for stolen legacy port.  This allows libata to guarantee that
index_of(ap) == ap->port_no == actual_device_port_no, and thus to
remove error-prone ap->hard_port_no.

As it's used only when one port of a legacy controller is reserved by
some other entity (e.g. IDE), the focus is on keeping the added *code*
complexity at minimum, so dummy port allocates all libata core
resources and acts as a normal port.  It just has all dummy port_ops.

This patch only implements dummy port.  The following patch will make
libata use it for stolen legacy ports.

Signed-off-by: Tejun Heo <htejun@gmail.com>

1 files changed, 8 insertions, 0 deletions

diff --git a/include/linux/libata.h b/include/linux/libata.h
index 4504776570e4..30bfe8f1666e 100644
--- a/include/linux/libata.h
+++ b/include/linux/libata.h
@@ -353,6 +353,7 @@ struct ata_probe_ent {
         struct ata_ioports      port[ATA_MAX_PORTS];
         unsigned int            n_ports;
         unsigned int            hard_port_no;
+        unsigned int            dummy_port_mask;
         unsigned int            pio_mask;
         unsigned int            mwdma_mask;
         unsigned int            udma_mask;
@@ -652,6 +653,8 @@ extern const unsigned long sata_deb_timing_normal[];
 extern const unsigned long sata_deb_timing_hotplug[];
 extern const unsigned long sata_deb_timing_long[];
 
+extern const struct ata_port_operations ata_dummy_port_ops;
+
 static inline const unsigned long *
 sata_ehc_deb_timing(struct ata_eh_context *ehc)
 {
@@ -661,6 +664,11 @@ sata_ehc_deb_timing(struct ata_eh_context *ehc)
                 return sata_deb_timing_normal;
 }
 
+static inline int ata_port_is_dummy(struct ata_port *ap)
+{
+        return ap->ops == &ata_dummy_port_ops;
+}
+
 extern void ata_port_probe(struct ata_port *);
 extern void __sata_phy_reset(struct ata_port *ap);
 extern void sata_phy_reset(struct ata_port *ap);