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seq: Clear UMP event flag for legacy apps

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It seems that some applications (at least Chrome WebMIDI) set random
bits to the flags of event packet, and this confuses as if they were
UMP-events, which are eventually filtered out.

Although it's a bug of applications, it's better to avoid the
regressions.  So this patch forcibly clears the UMP flag of the
incoming and outgoing events when the application is running in the
legacy mode (i.e. midi_version = 0).

Fixes: 2aefb5c41c ("seq: Add UMP support")
Closes: https://github.com/alsa-project/alsa-lib/issues/360
Signed-off-by: Takashi Iwai <tiwai@suse.de>
This commit is contained in:
Takashi Iwai 2023-11-06 16:27:11 +01:00
parent f202ec3c23
commit 2fca03e792
1 changed files with 10 additions and 0 deletions
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10
src/seq/seq.c
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@ -4161,6 +4161,13 @@ int snd_seq_event_output(snd_seq_t *seq, snd_seq_event_t *ev)
return result;
}
/* workaround for broken legacy apps that set UMP event bit unexpectedly */
static void clear_ump_for_legacy_apps(snd_seq_t *seq, snd_seq_event_t *ev)
{
if (!seq->midi_version && snd_seq_ev_is_ump(ev))
ev->flags &= ~SNDRV_SEQ_EVENT_UMP;
}
/**
* \brief output an event onto the lib buffer without draining buffer
* \param seq sequencer handle
@ -4178,6 +4185,7 @@ int snd_seq_event_output_buffer(snd_seq_t *seq, snd_seq_event_t *ev)
{
int len;
assert(seq && ev);
clear_ump_for_legacy_apps(seq, ev);
len = snd_seq_event_length(ev);
if (len < 0)
return -EINVAL;
@ -4238,6 +4246,7 @@ int snd_seq_event_output_direct(snd_seq_t *seq, snd_seq_event_t *ev)
ssize_t len;
void *buf;
clear_ump_for_legacy_apps(seq, ev);
len = snd_seq_event_length(ev);
if (len < 0)
return len;
@ -4374,6 +4383,7 @@ static int snd_seq_event_retrieve_buffer(snd_seq_t *seq, snd_seq_event_t **retp)
snd_seq_event_t *ev;
*retp = ev = (snd_seq_event_t *)(seq->ibuf + seq->ibufptr * packet_size);
clear_ump_for_legacy_apps(seq, ev);
seq->ibufptr++;
seq->ibuflen--;
if (! snd_seq_ev_is_variable(ev))