[PATCH] ASoC: use inline function for type safety in snd_soc_substream_to_rtd()

[Krzysztof Kozlowski]

A common pattern in sound drivers is getting 'struct snd_soc_pcm_runtime'
from 'struct snd_pcm_substream' opaque pointer private_data field with
snd_soc_substream_to_rtd().  However 'private_data' appears in several
other structures as well, including 'struct snd_compr_stream'.  The
field might not hold the same type for every structure, although seems
the case at least for 'struct snd_compr_stream', so code can easily make
a mistake by using macro for wrong structures.

Switch from macro to inline function, so such mistake will be build-time
detectable.

Signed-off-by: Krzysztof Kozlowski <krzysztof.kozlowski@xxxxxxxxxx>
---
 include/sound/soc.h | 8 ++++++--
 1 file changed, 6 insertions(+), 2 deletions(-)

diff --git a/include/sound/soc.h b/include/sound/soc.h
index 2a1b6c198547..cacaa92487a0 100644
--- a/include/sound/soc.h
+++ b/include/sound/soc.h
@@ -1215,8 +1215,12 @@ struct snd_soc_pcm_runtime {
 /* see soc_new_pcm_runtime()  */
 #define snd_soc_rtd_to_cpu(rtd, n)   (rtd)->dais[n]
 #define snd_soc_rtd_to_codec(rtd, n) (rtd)->dais[n + (rtd)->dai_link->num_cpus]
-#define snd_soc_substream_to_rtd(substream) \
-	(struct snd_soc_pcm_runtime *)snd_pcm_substream_chip(substream)
+
+static inline struct snd_soc_pcm_runtime *
+snd_soc_substream_to_rtd(const struct snd_pcm_substream *substream)
+{
+	return substream->private_data;
+}
 
 #define for_each_rtd_components(rtd, i, component)			\
 	for ((i) = 0, component = NULL;					\
-- 
2.43.0