1 files changed, 18 insertions, 5 deletions

diff --git a/include/linux/libata.h b/include/linux/libata.h
index eccc38e17568..46aa4ab64891 100644
--- a/include/linux/libata.h
+++ b/include/linux/libata.h
@@ -433,7 +433,7 @@ struct ata_host {
         void __iomem * const    *iomap;
         unsigned int            n_ports;
         void                    *private_data;
-        const struct ata_port_operations *ops;
+        struct ata_port_operations *ops;
         unsigned long           flags;
 #ifdef CONFIG_ATA_ACPI
         acpi_handle             acpi_handle;
@@ -602,7 +602,7 @@ struct ata_link {
 
 struct ata_port {
         struct Scsi_Host        *scsi_host; /* our co-allocated scsi host */
-        const struct ata_port_operations *ops;
+        struct ata_port_operations *ops;
         spinlock_t              *lock;
         unsigned long           flags;  /* ATA_FLAG_xxx */
         unsigned int            pflags; /* ATA_PFLAG_xxx */
@@ -664,6 +664,13 @@ struct ata_port {
         u8                      sector_buf[ATA_SECT_SIZE]; /* owned by EH */
 };
 
+/* The following initializer overrides a method to NULL whether one of
+ * its parent has the method defined or not.  This is equivalent to
+ * ERR_PTR(-ENOENT).  Unfortunately, ERR_PTR doesn't render a constant
+ * expression and thus can't be used as an initializer.
+ */
+#define ATA_OP_NULL             (void *)(unsigned long)(-ENOENT)
+
 struct ata_port_operations {
         /*
          * Command execution
@@ -733,6 +740,12 @@ struct ata_port_operations {
         void (*phy_reset)(struct ata_port *ap);
         void (*eng_timeout)(struct ata_port *ap);
         irq_handler_t irq_handler;
+
+        /*
+         * ->inherits must be the last field and all the preceding
+         * fields must be pointers.
+         */
+        const struct ata_port_operations        *inherits;
 };
 
 struct ata_port_info {
@@ -742,7 +755,7 @@ struct ata_port_info {
         unsigned long           pio_mask;
         unsigned long           mwdma_mask;
         unsigned long           udma_mask;
-        const struct ata_port_operations *port_ops;
+        struct ata_port_operations *port_ops;
         irq_handler_t           irq_handler;
         void                    *private_data;
 };
@@ -765,7 +778,7 @@ 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;
+extern struct ata_port_operations ata_dummy_port_ops;
 extern const struct ata_port_info ata_dummy_port_info;
 
 static inline const unsigned long *
@@ -812,7 +825,7 @@ extern int ata_host_activate(struct ata_host *host, int irq,
                              struct scsi_host_template *sht);
 extern void ata_host_detach(struct ata_host *host);
 extern void ata_host_init(struct ata_host *, struct device *,
-                          unsigned long, const struct ata_port_operations *);
+                          unsigned long, struct ata_port_operations *);
 extern int ata_scsi_detect(struct scsi_host_template *sht);
 extern int ata_scsi_ioctl(struct scsi_device *dev, int cmd, void __user *arg);
 extern int ata_scsi_queuecmd(struct scsi_cmnd *cmd, void (*done)(struct scsi_cmnd *));