ALSA: pcm: Allow exact buffer preallocation

A few drivers want to have rather the exact buffer preallocation at
the driver probe time and keep using it for the whole operations
without allowing dynamic buffer allocation.  For satisfying the
demands, this patch extends the managed buffer allocation API
slightly.

Namely, when 0 is passed to max argument of the allocation helper
functions snd_pcm_set_managed_buffer*(), it treats as if the fixed
size allocation of the given size.  If the pre-allocation fails in
this mode, the function returns now -ENOMEM.  Otherwise, i.e. max
argument is non-zero, the function never returns -ENOMEM but tries to
fall back to the smaller chunks and allows the dynamic allocation
later -- which is still the default behavior until now.

For more intuitive use, also two new helpers are added for handling
the fixed size buffer allocation, too: snd_pcm_set_fixed_buffer() and
snd_pcm_set_fixed_buffer_all().

Acked-by: Mark Brown <broonie@kernel.org>
Link: https://lore.kernel.org/r/20210802072815.13551-4-tiwai@suse.de
Signed-off-by: Takashi Iwai <tiwai@suse.de>

1 files changed, 42 insertions, 5 deletions

diff --git a/include/sound/pcm.h b/include/sound/pcm.h
index 938f36050a5e..33451f8ff755 100644
--- a/include/sound/pcm.h
+++ b/include/sound/pcm.h
@@ -1204,11 +1204,48 @@ void snd_pcm_lib_preallocate_pages_for_all(struct snd_pcm *pcm,
 int snd_pcm_lib_malloc_pages(struct snd_pcm_substream *substream, size_t size);
 int snd_pcm_lib_free_pages(struct snd_pcm_substream *substream);
 
-void snd_pcm_set_managed_buffer(struct snd_pcm_substream *substream, int type,
-				struct device *data, size_t size, size_t max);
-void snd_pcm_set_managed_buffer_all(struct snd_pcm *pcm, int type,
-				    struct device *data,
-				    size_t size, size_t max);
+int snd_pcm_set_managed_buffer(struct snd_pcm_substream *substream, int type,
+			       struct device *data, size_t size, size_t max);
+int snd_pcm_set_managed_buffer_all(struct snd_pcm *pcm, int type,
+				   struct device *data,
+				   size_t size, size_t max);
+
+/**
+ * snd_pcm_set_fixed_buffer - Preallocate and set up the fixed size PCM buffer
+ * @substream: the pcm substream instance
+ * @type: DMA type (SNDRV_DMA_TYPE_*)
+ * @data: DMA type dependent data
+ * @size: the requested pre-allocation size in bytes
+ *
+ * This is a variant of snd_pcm_set_managed_buffer(), but this pre-allocates
+ * only the given sized buffer and doesn't allow re-allocation nor dynamic
+ * allocation of a larger buffer unlike the standard one.
+ * The function may return -ENOMEM error, hence the caller must check it.
+ */
+static inline int __must_check
+snd_pcm_set_fixed_buffer(struct snd_pcm_substream *substream, int type,
+				 struct device *data, size_t size)
+{
+	return snd_pcm_set_managed_buffer(substream, type, data, size, 0);
+}
+
+/**
+ * snd_pcm_set_fixed_buffer_all - Preallocate and set up the fixed size PCM buffer
+ * @pcm: the pcm instance
+ * @type: DMA type (SNDRV_DMA_TYPE_*)
+ * @data: DMA type dependent data
+ * @size: the requested pre-allocation size in bytes
+ *
+ * Apply the set up of the fixed buffer via snd_pcm_set_fixed_buffer() for
+ * all substream.  If any of allocation fails, it returns -ENOMEM, hence the
+ * caller must check the return value.
+ */
+static inline int __must_check
+snd_pcm_set_fixed_buffer_all(struct snd_pcm *pcm, int type,
+			     struct device *data, size_t size)
+{
+	return snd_pcm_set_managed_buffer_all(pcm, type, data, size, 0);
+}
 
 int _snd_pcm_lib_alloc_vmalloc_buffer(struct snd_pcm_substream *substream,
 				      size_t size, gfp_t gfp_flags);