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ALSA: doc: Drop snd_dma_continuous_data() usages

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Update the documentation to follow the recent change of the memory
allocation helpers.  The macro snd_dma_continuous_data() is gone, and
the driver needs to set up the coherent dma mask for allocating in the
lower memory addresses, instead.

Link: https://lore.kernel.org/r/20220823115740.14123-6-tiwai@suse.de
Signed-off-by: Takashi Iwai <tiwai@suse.de>
This commit is contained in:
Takashi Iwai 2022-08-23 13:57:40 +02:00
parent dd164fbfdc
commit 0db78532ff
1 changed files with 8 additions and 13 deletions
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21
Documentation/sound/kernel-api/writing-an-alsa-driver.rst
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@ -3565,13 +3565,17 @@ given size.
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
``SNDRV_DMA_TYPE_DEV`` type.
For the continuous buffer unrelated to the
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_KERNEL`` 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()`.
If you need a restricted (lower) address, set up the coherent DMA mask
bits for the device, and pass the device pointer, like the normal
device memory allocations. For this type, it's still allowed to pass
NULL to the device pointer, too, if no address restriction is needed.
For the scatter-gather buffers, use ``SNDRV_DMA_TYPE_DEV_SG`` with the
device pointer (see the `Non-Contiguous Buffers`_ section).
@ -3811,15 +3815,6 @@ arguments here. Since each vmalloc call should succeed at any time,
we don't need to pre-allocate the buffers like other continuous
pages.
If you need the 32bit DMA allocation, pass the device pointer encoded
by :c:func:`snd_dma_continuous_data()` with ``GFP_KERNEL|__GFP_DMA32``
argument.
::
snd_pcm_set_managed_buffer_all(pcm, SNDRV_DMA_TYPE_VMALLOC,
snd_dma_continuous_data(GFP_KERNEL | __GFP_DMA32), 0, 0);
Proc Interface
==============