diff --git a/Documentation/DocBook/libata.tmpl b/Documentation/DocBook/libata.tmpl
index 773ae9fd99dc..41053aed41f4 100644
--- a/Documentation/DocBook/libata.tmpl
+++ b/Documentation/DocBook/libata.tmpl
@@ -14,7 +14,7 @@
   </authorgroup>
 
   <copyright>
-   <year>2003</year>
+   <year>2003-2005</year>
    <holder>Jeff Garzik</holder>
   </copyright>
 
@@ -145,14 +145,25 @@ void (*exec_command)(struct ata_port *ap, struct ata_taskfile *tf);
 	</para>
 
 	<programlisting>
-u8   (*check_status)(struct ata_port *ap);
-void (*dev_select)(struct ata_port *ap, unsigned int device);
+int (*check_atapi_dma) (struct ata_queued_cmd *qc);
 	</programlisting>
 
 	<para>
-	Reads the Status ATA shadow register from hardware.  On some
-	hardware, this has the side effect of clearing the interrupt
-	condition.
+Allow low-level driver to filter ATA PACKET commands, returning a status
+indicating whether or not it is OK to use DMA for the supplied PACKET
+command.
+	</para>
+
+	<programlisting>
+u8   (*check_status)(struct ata_port *ap);
+u8   (*check_altstatus)(struct ata_port *ap);
+u8   (*check_err)(struct ata_port *ap);
+	</programlisting>
+
+	<para>
+	Reads the Status/AltStatus/Error ATA shadow register from
+	hardware.  On some hardware, reading the Status register has
+	the side effect of clearing the interrupt condition.
 	</para>
 
 	<programlisting>
@@ -162,7 +173,8 @@ void (*dev_select)(struct ata_port *ap, unsigned int device);
 	<para>
 	Issues the low-level hardware command(s) that causes one of N
 	hardware devices to be considered 'selected' (active and
-	available for use) on the ATA bus.
+	available for use) on the ATA bus.  This generally has no
+meaning on FIS-based devices.
 	</para>
 
 	<programlisting>
@@ -180,12 +192,20 @@ void (*phy_reset) (struct ata_port *ap);
 	<programlisting>
 void (*bmdma_setup) (struct ata_queued_cmd *qc);
 void (*bmdma_start) (struct ata_queued_cmd *qc);
+void (*bmdma_stop) (struct ata_port *ap);
+u8   (*bmdma_status) (struct ata_port *ap);
 	</programlisting>
 
 	<para>
-	When setting up an IDE BMDMA transaction, these hooks arm
-	(->bmdma_setup) and fire (->bmdma_start) the hardware's DMA
-	engine.
+When setting up an IDE BMDMA transaction, these hooks arm
+(->bmdma_setup), fire (->bmdma_start), and halt (->bmdma_stop)
+the hardware's DMA engine.  ->bmdma_status is used to read the standard
+PCI IDE DMA Status register.
+	</para>
+
+	<para>
+These hooks are typically either no-ops, or simply not implemented, in
+FIS-based drivers.
 	</para>
 
 	<programlisting>
@@ -205,9 +225,7 @@ int (*qc_issue) (struct ata_queued_cmd *qc);
 	->qc_issue is used to make a command active, once the hardware
 	and S/G tables have been prepared.  IDE BMDMA drivers use the
 	helper function ata_qc_issue_prot() for taskfile protocol-based
-	dispatch.  More advanced drivers roll their own ->qc_issue
-	implementation, using this as the "issue new ATA command to
-	hardware" hook.
+	dispatch.  More advanced drivers implement their own ->qc_issue.
 	</para>
 
 	<programlisting>
@@ -215,8 +233,10 @@ void (*eng_timeout) (struct ata_port *ap);
 	</programlisting>
 
 	<para>
-	This is a high level error handling function, called from the
-	error handling thread, when a command times out.
+This is a high level error handling function, called from the
+error handling thread, when a command times out.  Most newer
+hardware will implement its own error handling code here.  IDE BMDMA
+drivers may use the helper function ata_eng_timeout().
 	</para>
 
 	<programlisting>
@@ -255,15 +275,15 @@ void (*host_stop) (struct ata_host_set *host_set);
 	tasks.  
 	</para>
 	<para>
-	->host_stop() is called when the rmmod or hot unplug process
-	begins.  The hook must stop all hardware interrupts, DMA
-	engines, etc.
-	</para>
-	<para>
 	->port_stop() is called after ->host_stop().  It's sole function
 	is to release DMA/memory resources, now that they are no longer
 	actively being used.
 	</para>
+	<para>
+	->host_stop() is called after all ->port_stop() calls
+have completed.  The hook must finalize hardware shutdown, release DMA
+and other resources, etc.
+	</para>
 
      </sect1>
   </chapter>
diff --git a/drivers/scsi/libata-core.c b/drivers/scsi/libata-core.c
index 63d3f70d06e1..4d707d06a5d1 100644
--- a/drivers/scsi/libata-core.c
+++ b/drivers/scsi/libata-core.c
@@ -1241,10 +1241,14 @@ void ata_port_probe(struct ata_port *ap)
 }
 
 /**
- *	__sata_phy_reset -
- *	@ap:
+ *	__sata_phy_reset - Wake/reset a low-level SATA PHY
+ *	@ap: SATA port associated with target SATA PHY.
  *
- *	LOCKING:
+ *	This function issues commands to standard SATA Sxxx
+ *	PHY registers, to wake up the phy (and device), and
+ *	clear any reset condition.
+ *
+ *	LOCKING: None.  Serialized during ata_bus_probe().
  *
  */
 void __sata_phy_reset(struct ata_port *ap)
@@ -1289,10 +1293,13 @@ void __sata_phy_reset(struct ata_port *ap)
 }
 
 /**
- *	__sata_phy_reset -
- *	@ap:
+ *	sata_phy_reset - Reset SATA bus.
+ *	@ap: SATA port associated with target SATA PHY.
  *
- *	LOCKING:
+ *	This function resets the SATA bus, and then probes
+ *	the bus for devices.
+ *
+ *	LOCKING: None.  Serialized during ata_bus_probe().
  *
  */
 void sata_phy_reset(struct ata_port *ap)
@@ -1304,10 +1311,16 @@ void sata_phy_reset(struct ata_port *ap)
 }
 
 /**
- *	ata_port_disable -
- *	@ap:
+ *	ata_port_disable - Disable port.
+ *	@ap: Port to be disabled.
  *
- *	LOCKING:
+ *	Modify @ap data structure such that the system
+ *	thinks that the entire port is disabled, and should
+ *	never attempt to probe or communicate with devices
+ *	on this port.
+ *
+ *	LOCKING: host_set lock, or some other form of
+ *	serialization.
  */
 
 void ata_port_disable(struct ata_port *ap)
@@ -1416,7 +1429,9 @@ static void ata_host_set_dma(struct ata_port *ap, u8 xfer_mode,
  *	ata_set_mode - Program timings and issue SET FEATURES - XFER
  *	@ap: port on which timings will be programmed
  *
- *	LOCKING:
+ *	Set ATA device disk transfer mode (PIO3, UDMA6, etc.).
+ *
+ *	LOCKING: None.  Serialized during ata_bus_probe().
  *
  */
 static void ata_set_mode(struct ata_port *ap)
@@ -1467,7 +1482,10 @@ static void ata_set_mode(struct ata_port *ap)
  *	@tmout_pat: impatience timeout
  *	@tmout: overall timeout
  *
- *	LOCKING:
+ *	Sleep until ATA Status register bit BSY clears,
+ *	or a timeout occurs.
+ *
+ *	LOCKING: None.
  *
  */
 
@@ -1556,7 +1574,7 @@ static void ata_bus_post_reset(struct ata_port *ap, unsigned int devmask)
  *	ata_bus_edd -
  *	@ap:
  *
- *	LOCKING:
+ *	LOCKING: None.  Serialized during ata_bus_probe().
  *
  */
 
@@ -1909,7 +1927,10 @@ static int ata_choose_xfer_mode(struct ata_port *ap,
  *	@ap: Port associated with device @dev
  *	@dev: Device to which command will be sent
  *
- *	LOCKING:
+ *	Issue SET FEATURES - XFER MODE command to device @dev
+ *	on port @ap.
+ *
+ *	LOCKING: None.  Serialized during ata_bus_probe().
  */
 
 static void ata_dev_set_xfermode(struct ata_port *ap, struct ata_device *dev)
@@ -1981,7 +2002,11 @@ static void ata_sg_clean(struct ata_queued_cmd *qc)
  *	ata_fill_sg - Fill PCI IDE PRD table
  *	@qc: Metadata associated with taskfile to be transferred
  *
+ *	Fill PCI IDE PRD (scatter-gather) table with segments
+ *	associated with the current disk command.
+ *
  *	LOCKING:
+ *	spin_lock_irqsave(host_set lock)
  *
  */
 static void ata_fill_sg(struct ata_queued_cmd *qc)
@@ -2028,6 +2053,10 @@ static void ata_fill_sg(struct ata_queued_cmd *qc)
  *	ata_check_atapi_dma - Check whether ATAPI DMA can be supported
  *	@qc: Metadata associated with taskfile to check
  *
+ *	Allow low-level driver to filter ATA PACKET commands, returning
+ *	a status indicating whether or not it is OK to use DMA for the
+ *	supplied PACKET command.
+ *
  *	LOCKING:
  *	RETURNS: 0 when ATAPI DMA can be used
  *               nonzero otherwise
@@ -2046,6 +2075,8 @@ int ata_check_atapi_dma(struct ata_queued_cmd *qc)
  *	ata_qc_prep - Prepare taskfile for submission
  *	@qc: Metadata associated with taskfile to be prepared
  *
+ *	Prepare ATA taskfile for submission.
+ *
  *	LOCKING:
  *	spin_lock_irqsave(host_set lock)
  */