ALSA: memalloc: Allow NULL device for SNDRV_DMA_TYPE_CONTINUOUS type

[linux-2.6-block.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 6b154dbb02cc76eb991c809af4bec52528114c84..5385618fd881433ff969078278d1f5a4e5e06ca5 100644 (file)
--- a/Documentation/sound/kernel-api/writing-an-alsa-driver.rst
+++ b/Documentation/sound/kernel-api/writing-an-alsa-driver.rst
@@ -324,7 +324,7 @@ to details explained in the following section.
               strcpy(card->driver, "My Chip");
               strcpy(card->shortname, "My Own Chip 123");
               sprintf(card->longname, "%s at 0x%lx irq %i",
-                      card->shortname, chip->ioport, chip->irq);
+                      card->shortname, chip->port, chip->irq);
 
               /* (5) */
               .... /* implemented later */
@@ -437,7 +437,7 @@ Since each component can be properly freed, the single
   strcpy(card->driver, "My Chip");
   strcpy(card->shortname, "My Own Chip 123");
   sprintf(card->longname, "%s at 0x%lx irq %i",
-          card->shortname, chip->ioport, chip->irq);
+          card->shortname, chip->port, chip->irq);
 
 The driver field holds the minimal ID string of the chip. This is used
 by alsa-lib's configurator, so keep it simple but unique. Even the
@@ -3523,12 +3523,14 @@ The second argument (type) and the third argument (device pointer) are
 dependent on the bus. For normal devices, pass the device pointer
 (typically identical as ``card->dev``) to the third argument with
 ``SNDRV_DMA_TYPE_DEV`` type. For the continuous buffer unrelated to the
-bus can be pre-allocated with ``SNDRV_DMA_TYPE_CONTINUOUS`` type and the
-``snd_dma_continuous_data(GFP_KERNEL)`` device pointer, where
-``GFP_KERNEL`` is the kernel allocation flag to use. For the
-scatter-gather buffers, use ``SNDRV_DMA_TYPE_DEV_SG`` with the device
-pointer (see the `Non-Contiguous Buffers`_
-section).
+bus can be pre-allocated with ``SNDRV_DMA_TYPE_CONTINUOUS`` type.
+You can pass NULL to the device pointer in that case, which is the
+default mode implying to allocate with ``GFP_KRENEL`` flag.
+If you need a different GFP flag, you can pass it by encoding the flag
+into the device pointer via a special macro
+:c:func:`snd_dma_continuous_data()`.
+For the scatter-gather buffers, use ``SNDRV_DMA_TYPE_DEV_SG`` with the
+device pointer (see the `Non-Contiguous Buffers`_ section).
 
 Once the buffer is pre-allocated, you can use the allocator in the
 ``hw_params`` callback: