ALSA: docs: Add description about ack callback -EPIPE error handling

[linux-2.6-microblaze.git] / Documentation / sound / kernel-api / writing-an-alsa-driver.rst

diff --git a/Documentation/sound/kernel-api/writing-an-alsa-driver.rst b/Documentation/sound/kernel-api/writing-an-alsa-driver.rst
index 5c9523b..6b8f349 100644 (file)
--- a/Documentation/sound/kernel-api/writing-an-alsa-driver.rst
+++ b/Documentation/sound/kernel-api/writing-an-alsa-driver.rst
@@ -2137,6 +2137,10 @@ This callback is also not mandatory. This callback is called when the
 emu10k1-fx and cs46xx need to track the current ``appl_ptr`` for the
 internal buffer, and this callback is useful only for such a purpose.
 
+The callback function may return 0 or a negative error. When the
+return value is ``-EPIPE``, PCM core treats as a buffer XRUN happens,
+and changes the state to ``SNDRV_PCM_STATE_XRUN`` automatically.
+
 This callback is atomic as default.
 
 page callback