linux-kernel - [PATCH] ASoC: meson: cards: select SND_DYNAMIC

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Date: Fri, 26 Apr 2024 15:41:47 +0200
From: Jerome Brunet <jbrunet@...libre.com>
To: Mark Brown <broonie@...nel.org>,
	Liam Girdwood <lgirdwood@...il.com>
Cc: Jerome Brunet <jbrunet@...libre.com>,
	alsa-devel@...a-project.org,
	linux-kernel@...r.kernel.org,
	linux-amlogic@...ts.infradead.org
Subject: [PATCH] ASoC: meson: cards: select SND_DYNAMIC_MINORS

Amlogic sound cards do create a lot of pcm interfaces, possibly more than
8. Some pcm interfaces are internal (like DPCM backends and c2c) and not
exposed to userspace.

Those interfaces still increase the number passed to snd_find_free_minor(),
which eventually exceeds 8 causing -EBUSY error on card registration if
CONFIG_SND_DYNAMIC_MINORS=n and the interface is exposed to userspace.

select CONFIG_SND_DYNAMIC_MINORS for Amlogic cards to avoid the problem.

Fixes: 7864a79f37b5 ("ASoC: meson: add axg sound card support")
Signed-off-by: Jerome Brunet <jbrunet@...libre.com>
---

NOTE: This problem was found while toying with a minimal configuration
which disabled CONFIG_SND_DYNAMIC_MINORS and DT overlays. Overlays
prepend nodes instead of doing append. This changes the order in which
the links are parsed by the card driver, which in turn changes the pcm
numbers. The userpace pcm number then got over 8 triggering the problem.

 sound/soc/meson/Kconfig | 1 +
 1 file changed, 1 insertion(+)

diff --git a/sound/soc/meson/Kconfig b/sound/soc/meson/Kconfig
index b93ea33739f2..6458d5dc4902 100644
--- a/sound/soc/meson/Kconfig
+++ b/sound/soc/meson/Kconfig
@@ -99,6 +99,7 @@ config SND_MESON_AXG_PDM

 config SND_MESON_CARD_UTILS
 	tristate
+	select SND_DYNAMIC_MINORS

 config SND_MESON_CODEC_GLUE
 	tristate
-- 
2.43.0