From 052a356856a441c2dec6c2bd37b7bb7908c79289 Mon Sep 17 00:00:00 2001
From: Takashi Iwai <tiwai@suse.de>
Date: Tue, 13 Apr 2010 12:55:09 +0200
Subject: [PATCH] --- yaml --- r: 193205 b: refs/heads/master c:
 c56a3b18475b0f93b484c25162c1379f5aee367a h: refs/heads/master i:   193203:
 678e0b9b97111e55a207ffc18e40fc2278c3c549 v: v3

---
 [refs]                                        |  2 +-
 .../DocBook/writing-an-alsa-driver.tmpl       | 27 ++++++++++++-------
 2 files changed, 18 insertions(+), 11 deletions(-)

diff --git a/[refs] b/[refs]
index f4aa4755318c..63cd6077cd0f 100644
--- a/[refs]
+++ b/[refs]
@@ -1,2 +1,2 @@
 ---
-refs/heads/master: 02f4865fa415a87de28cc8c2e4d798ff46be1cf8
+refs/heads/master: c56a3b18475b0f93b484c25162c1379f5aee367a
diff --git a/trunk/Documentation/DocBook/writing-an-alsa-driver.tmpl b/trunk/Documentation/DocBook/writing-an-alsa-driver.tmpl
index 0d0f7b4d4b1a..0ba149de2608 100644
--- a/trunk/Documentation/DocBook/writing-an-alsa-driver.tmpl
+++ b/trunk/Documentation/DocBook/writing-an-alsa-driver.tmpl
@@ -5518,34 +5518,41 @@ struct _snd_pcm_runtime {
 ]]>
         </programlisting>
       </informalexample>
+
+      For the raw data, <structfield>size</structfield> field must be
+      set properly.  This specifies the maximum size of the proc file access.
     </para>
 
     <para>
-      The callback is much more complicated than the text-file
-      version. You need to use a low-level I/O functions such as
+      The read/write callbacks of raw mode are more direct than the text mode.
+      You need to use a low-level I/O functions such as
       <function>copy_from/to_user()</function> to transfer the
       data.
 
       <informalexample>
         <programlisting>
 <![CDATA[
-  static long my_file_io_read(struct snd_info_entry *entry,
+  static ssize_t my_file_io_read(struct snd_info_entry *entry,
                               void *file_private_data,
                               struct file *file,
                               char *buf,
-                              unsigned long count,
-                              unsigned long pos)
+                              size_t count,
+                              loff_t pos)
   {
-          long size = count;
-          if (pos + size > local_max_size)
-                  size = local_max_size - pos;
-          if (copy_to_user(buf, local_data + pos, size))
+          if (copy_to_user(buf, local_data + pos, count))
                   return -EFAULT;
-          return size;
+          return count;
   }
 ]]>
         </programlisting>
       </informalexample>
+
+      If the size of the info entry has been set up properly,
+      <structfield>count</structfield> and <structfield>pos</structfield> are
+      guaranteed to fit within 0 and the given size.
+      You don't have to check the range in the callbacks unless any
+      other condition is required.
+
     </para>
 
   </chapter>