1 files changed, 43 insertions, 4 deletions

diff --git a/Documentation/DocBook/libata.tmpl b/Documentation/DocBook/libata.tmpl
index d260d92089ad..5bcbb6ee3bc0 100644
--- a/Documentation/DocBook/libata.tmpl
+++ b/Documentation/DocBook/libata.tmpl
@@ -120,14 +120,27 @@ void (*dev_config) (struct ata_port *, struct ata_device *);
         <programlisting>
 void (*set_piomode) (struct ata_port *, struct ata_device *);
 void (*set_dmamode) (struct ata_port *, struct ata_device *);
-void (*post_set_mode) (struct ata_port *ap);
+void (*post_set_mode) (struct ata_port *);
+unsigned int (*mode_filter) (struct ata_port *, struct ata_device *, unsigned int);
         </programlisting>
 
         <para>
         Hooks called prior to the issue of SET FEATURES - XFER MODE
-        command.  dev->pio_mode is guaranteed to be valid when
-        ->set_piomode() is called, and dev->dma_mode is guaranteed to be
-        valid when ->set_dmamode() is called.  ->post_set_mode() is
+        command.  The optional ->mode_filter() hook is called when libata
+        has built a mask of the possible modes. This is passed to the 
+        ->mode_filter() function which should return a mask of valid modes
+        after filtering those unsuitable due to hardware limits. It is not
+        valid to use this interface to add modes.
+        </para>
+        <para>
+        dev->pio_mode and dev->dma_mode are guaranteed to be valid when
+        ->set_piomode() and when ->set_dmamode() is called. The timings for
+        any other drive sharing the cable will also be valid at this point.
+        That is the library records the decisions for the modes of each
+        drive on a channel before it attempts to set any of them.
+        </para>
+        <para>
+        ->post_set_mode() is
         called unconditionally, after the SET FEATURES - XFER MODE
         command completes successfully.
         </para>
@@ -230,6 +243,32 @@ void (*dev_select)(struct ata_port *ap, unsigned int device);
 
         </sect2>
 
+        <sect2><title>Private tuning method</title>
+        <programlisting>
+void (*set_mode) (struct ata_port *ap);
+        </programlisting>
+
+        <para>
+        By default libata performs drive and controller tuning in
+        accordance with the ATA timing rules and also applies blacklists
+        and cable limits. Some controllers need special handling and have
+        custom tuning rules, typically raid controllers that use ATA
+        commands but do not actually do drive timing.
+        </para>
+
+        <warning>
+        <para>
+        This hook should not be used to replace the standard controller
+        tuning logic when a controller has quirks. Replacing the default
+        tuning logic in that case would bypass handling for drive and
+        bridge quirks that may be important to data reliability. If a
+        controller needs to filter the mode selection it should use the
+        mode_filter hook instead.
+        </para>
+        </warning>
+
+        </sect2>
+
         <sect2><title>Reset ATA bus</title>
         <programlisting>
 void (*phy_reset) (struct ata_port *ap);