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author | Michal Marek <mmarek@suse.cz> | 2010-08-04 08:05:07 -0400 |
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committer | Michal Marek <mmarek@suse.cz> | 2010-08-04 08:05:07 -0400 |
commit | 7a996d3ab150bb0e1b71fa182f70199a703efdd1 (patch) | |
tree | 96a36947d90c9b96580899abd38cb3b70cd9d40b /Documentation/DocBook/writing-an-alsa-driver.tmpl | |
parent | 7cf3d73b4360e91b14326632ab1aeda4cb26308d (diff) | |
parent | 9fe6206f400646a2322096b56c59891d530e8d51 (diff) |
Merge commit 'v2.6.35' into kbuild/kconfig
Conflicts:
scripts/kconfig/Makefile
Diffstat (limited to 'Documentation/DocBook/writing-an-alsa-driver.tmpl')
-rw-r--r-- | Documentation/DocBook/writing-an-alsa-driver.tmpl | 27 |
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 { | |||
5518 | ]]> | 5518 | ]]> |
5519 | </programlisting> | 5519 | </programlisting> |
5520 | </informalexample> | 5520 | </informalexample> |
5521 | |||
5522 | For the raw data, <structfield>size</structfield> field must be | ||
5523 | set properly. This specifies the maximum size of the proc file access. | ||
5521 | </para> | 5524 | </para> |
5522 | 5525 | ||
5523 | <para> | 5526 | <para> |
5524 | The callback is much more complicated than the text-file | 5527 | The read/write callbacks of raw mode are more direct than the text mode. |
5525 | version. You need to use a low-level I/O functions such as | 5528 | You need to use a low-level I/O functions such as |
5526 | <function>copy_from/to_user()</function> to transfer the | 5529 | <function>copy_from/to_user()</function> to transfer the |
5527 | data. | 5530 | data. |
5528 | 5531 | ||
5529 | <informalexample> | 5532 | <informalexample> |
5530 | <programlisting> | 5533 | <programlisting> |
5531 | <![CDATA[ | 5534 | <![CDATA[ |
5532 | static long my_file_io_read(struct snd_info_entry *entry, | 5535 | static ssize_t my_file_io_read(struct snd_info_entry *entry, |
5533 | void *file_private_data, | 5536 | void *file_private_data, |
5534 | struct file *file, | 5537 | struct file *file, |
5535 | char *buf, | 5538 | char *buf, |
5536 | unsigned long count, | 5539 | size_t count, |
5537 | unsigned long pos) | 5540 | loff_t pos) |
5538 | { | 5541 | { |
5539 | long size = count; | 5542 | if (copy_to_user(buf, local_data + pos, count)) |
5540 | if (pos + size > local_max_size) | ||
5541 | size = local_max_size - pos; | ||
5542 | if (copy_to_user(buf, local_data + pos, size)) | ||
5543 | return -EFAULT; | 5543 | return -EFAULT; |
5544 | return size; | 5544 | return count; |
5545 | } | 5545 | } |
5546 | ]]> | 5546 | ]]> |
5547 | </programlisting> | 5547 | </programlisting> |
5548 | </informalexample> | 5548 | </informalexample> |
5549 | |||
5550 | If the size of the info entry has been set up properly, | ||
5551 | <structfield>count</structfield> and <structfield>pos</structfield> are | ||
5552 | guaranteed to fit within 0 and the given size. | ||
5553 | You don't have to check the range in the callbacks unless any | ||
5554 | other condition is required. | ||
5555 | |||
5549 | </para> | 5556 | </para> |
5550 | 5557 | ||
5551 | </chapter> | 5558 | </chapter> |