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authorDavid Henningsson <david.henningsson@canonical.com>2013-05-08 15:33:11 +0200
committerTakashi Iwai <tiwai@suse.de>2013-05-08 15:43:56 +0200
commitd24f5a9ad9febffa53b1d3fcdf36c9a2283d848e (patch)
treee5e0ecd75cfae2e45f964a05e55b9d7f874e39da /include/sound/tlv.h
parent17df3f55652f7ea8fb1197b5c32e227b3da9f215 (diff)
downloadlinux-d24f5a9ad9febffa53b1d3fcdf36c9a2283d848e.tar.bz2
ALSA: Add comment for control TLV API
Userspace is not meant to have to handle all strange dB ranges, so add a specification comment. Signed-off-by: David Henningsson <david.henningsson@canonical.com> Signed-off-by: Takashi Iwai <tiwai@suse.de>
Diffstat (limited to 'include/sound/tlv.h')
-rw-r--r--include/sound/tlv.h6
1 files changed, 5 insertions, 1 deletions
diff --git a/include/sound/tlv.h b/include/sound/tlv.h
index 28c65e1ada21..e11e179420a1 100644
--- a/include/sound/tlv.h
+++ b/include/sound/tlv.h
@@ -74,7 +74,11 @@
#define DECLARE_TLV_DB_LINEAR(name, min_dB, max_dB) \
unsigned int name[] = { TLV_DB_LINEAR_ITEM(min_dB, max_dB) }
-/* dB range container */
+/* dB range container:
+ * Items in dB range container must be ordered by their values and by their
+ * dB values. This implies that larger values must correspond with larger
+ * dB values (which is also required for all other mixer controls).
+ */
/* Each item is: <min> <max> <TLV> */
#define TLV_DB_RANGE_ITEM(...) \
TLV_ITEM(SNDRV_CTL_TLVT_DB_RANGE, __VA_ARGS__)