ALSA: document that struct __snd_pcm_mmap_control64 is messed up

I'm not the first one to run into this, see e.g.
https://lore.kernel.org/all/29QBMJU8DE71E.2YZSH8IHT5HMH@mforney.org/

Signed-off-by: Oswald Buddenhagen <oswald.buddenhagen@gmx.de>
Link: https://lore.kernel.org/r/20230406132521.2252019-1-oswald.buddenhagen@gmx.de
Signed-off-by: Takashi Iwai <tiwai@suse.de>

diff --git a/include/uapi/sound/asound.h b/include/uapi/sound/asound.h
index de6810e94abed3e91de3ef42d1eaca0353c1b8d3..7eecc99ddef7d3782496fd2f4e931154c61f46df 100644 (file)
--- a/include/uapi/sound/asound.h
+++ b/include/uapi/sound/asound.h
@@ -570,7 +570,8 @@ struct __snd_pcm_mmap_status64 {
 struct __snd_pcm_mmap_control64 {
        __pad_before_uframe __pad1;
        snd_pcm_uframes_t appl_ptr;      /* RW: appl ptr (0...boundary-1) */
-       __pad_before_uframe __pad2;
+       __pad_before_uframe __pad2;      // This should be __pad_after_uframe, but binary
+                                        // backwards compatibility constraints prevent a fix.
 
        __pad_before_uframe __pad3;
        snd_pcm_uframes_t  avail_min;    /* RW: min available frames for wakeup */