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authorGrant Likely <grant.likely@secretlab.ca>2010-05-22 10:36:56 +0400
committerGrant Likely <grant.likely@secretlab.ca>2010-05-22 10:36:56 +0400
commitcf9b59e9d3e008591d1f54830f570982bb307a0d (patch)
tree113478ce8fd8c832ba726ffdf59b82cb46356476 /Documentation/DocBook/writing-an-alsa-driver.tmpl
parent44504b2bebf8b5823c59484e73096a7d6574471d (diff)
parentf4b87dee923342505e1ddba8d34ce9de33e75050 (diff)
downloadlinux-cf9b59e9d3e008591d1f54830f570982bb307a0d.tar.xz
Merge remote branch 'origin' into secretlab/next-devicetree
Merging in current state of Linus' tree to deal with merge conflicts and build failures in vio.c after merge. Conflicts: drivers/i2c/busses/i2c-cpm.c drivers/i2c/busses/i2c-mpc.c drivers/net/gianfar.c Also fixed up one line in arch/powerpc/kernel/vio.c to use the correct node pointer. Signed-off-by: Grant Likely <grant.likely@secretlab.ca>
Diffstat (limited to 'Documentation/DocBook/writing-an-alsa-driver.tmpl')
-rw-r--r--Documentation/DocBook/writing-an-alsa-driver.tmpl27
1 files changed, 17 insertions, 10 deletions
diff --git a/Documentation/DocBook/writing-an-alsa-driver.tmpl b/Documentation/DocBook/writing-an-alsa-driver.tmpl
index 0d0f7b4d4b1a..0ba149de2608 100644
--- a/Documentation/DocBook/writing-an-alsa-driver.tmpl
+++ b/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>