From: Takashi Iwai Date: Tue, 31 Dec 2024 11:55:18 +0000 (+0100) Subject: ALSA: seq: oss: Send fragmented SysEx messages immediately X-Git-Tag: v6.14-rc1~111^2~42 X-Git-Url: http://git.ipfire.org/?a=commitdiff_plain;h=20ce9ded8c596d046813762e362929dfbcb28567;p=thirdparty%2Fkernel%2Flinux.git ALSA: seq: oss: Send fragmented SysEx messages immediately The recent bug report spotted on the old OSS sequencer code that tries to combine incoming SysEx messages to a single sequencer event. This is good, per se, but it has more demerits: - The sysex message delivery is delayed until the very last event - The use of internal buffer forced the serialization The recent fix in commit 0179488ca992 ("ALSA: seq: oss: Fix races at processing SysEx messages") addressed the latter, but a better fix is to handle the sysex messages immediately, i.e. just send each incoming fragmented sysex message as is. And this patch implements that. This resulted in a significant cleanup as well. Note that the only caller of snd_seq_oss_synth_sysex() is snd_seq_oss_process_event(), and all its callers dispatch the event immediately, so we can just put the passed buffer pointer to the event record to be handled. Reported-and-tested-by: Kun Hu Link: https://lore.kernel.org/2B7E93E4-B13A-4AE4-8E87-306A8EE9BBB7@m.fudan.edu.cn Link: https://patch.msgid.link/20241231115523.15796-1-tiwai@suse.de Signed-off-by: Takashi Iwai --- diff --git a/sound/core/seq/oss/seq_oss_device.h b/sound/core/seq/oss/seq_oss_device.h index 98dd20b429764..c0b1cce127a33 100644 --- a/sound/core/seq/oss/seq_oss_device.h +++ b/sound/core/seq/oss/seq_oss_device.h @@ -55,7 +55,6 @@ struct seq_oss_chinfo { struct seq_oss_synthinfo { struct snd_seq_oss_arg arg; struct seq_oss_chinfo *ch; - struct seq_oss_synth_sysex *sysex; int nr_voices; int opened; int is_midi; diff --git a/sound/core/seq/oss/seq_oss_synth.c b/sound/core/seq/oss/seq_oss_synth.c index 51ee4c00a8431..02a90c960992e 100644 --- a/sound/core/seq/oss/seq_oss_synth.c +++ b/sound/core/seq/oss/seq_oss_synth.c @@ -26,13 +26,6 @@ * definition of synth info records */ -/* sysex buffer */ -struct seq_oss_synth_sysex { - int len; - int skip; - unsigned char buf[MAX_SYSEX_BUFLEN]; -}; - /* synth info */ struct seq_oss_synth { int seq_device; @@ -66,7 +59,6 @@ static struct seq_oss_synth midi_synth_dev = { }; static DEFINE_SPINLOCK(register_lock); -static DEFINE_MUTEX(sysex_mutex); /* * prototypes @@ -319,8 +311,6 @@ snd_seq_oss_synth_cleanup(struct seq_oss_devinfo *dp) } snd_use_lock_free(&rec->use_lock); } - kfree(info->sysex); - info->sysex = NULL; kfree(info->ch); info->ch = NULL; } @@ -396,8 +386,6 @@ snd_seq_oss_synth_reset(struct seq_oss_devinfo *dp, int dev) info = get_synthinfo_nospec(dp, dev); if (!info || !info->opened) return; - if (info->sysex) - info->sysex->len = 0; /* reset sysex */ reset_channels(info); if (info->is_midi) { if (midi_synth_dev.opened <= 0) @@ -409,8 +397,6 @@ snd_seq_oss_synth_reset(struct seq_oss_devinfo *dp, int dev) dp->file_mode) < 0) { midi_synth_dev.opened--; info->opened = 0; - kfree(info->sysex); - info->sysex = NULL; kfree(info->ch); info->ch = NULL; } @@ -483,64 +469,26 @@ snd_seq_oss_synth_info(struct seq_oss_devinfo *dp, int dev) /* * receive OSS 6 byte sysex packet: - * the full sysex message will be sent if it reaches to the end of data - * (0xff). + * the event is filled and prepared for sending immediately + * (i.e. sysex messages are fragmented) */ int snd_seq_oss_synth_sysex(struct seq_oss_devinfo *dp, int dev, unsigned char *buf, struct snd_seq_event *ev) { - int i, send; - unsigned char *dest; - struct seq_oss_synth_sysex *sysex; - struct seq_oss_synthinfo *info; + unsigned char *p; + int len = 6; - info = snd_seq_oss_synth_info(dp, dev); - if (!info) - return -ENXIO; + p = memchr(buf, 0xff, 6); + if (p) + len = p - buf + 1; - guard(mutex)(&sysex_mutex); - sysex = info->sysex; - if (sysex == NULL) { - sysex = kzalloc(sizeof(*sysex), GFP_KERNEL); - if (sysex == NULL) - return -ENOMEM; - info->sysex = sysex; - } - - send = 0; - dest = sysex->buf + sysex->len; - /* copy 6 byte packet to the buffer */ - for (i = 0; i < 6; i++) { - if (buf[i] == 0xff) { - send = 1; - break; - } - dest[i] = buf[i]; - sysex->len++; - if (sysex->len >= MAX_SYSEX_BUFLEN) { - sysex->len = 0; - sysex->skip = 1; - break; - } - } - - if (sysex->len && send) { - if (sysex->skip) { - sysex->skip = 0; - sysex->len = 0; - return -EINVAL; /* skip */ - } - /* copy the data to event record and send it */ - ev->flags = SNDRV_SEQ_EVENT_LENGTH_VARIABLE; - if (snd_seq_oss_synth_addr(dp, dev, ev)) - return -EINVAL; - ev->data.ext.len = sysex->len; - ev->data.ext.ptr = sysex->buf; - sysex->len = 0; - return 0; - } - - return -EINVAL; /* skip */ + /* copy the data to event record and send it */ + if (snd_seq_oss_synth_addr(dp, dev, ev)) + return -EINVAL; + ev->flags = SNDRV_SEQ_EVENT_LENGTH_VARIABLE; + ev->data.ext.len = len; + ev->data.ext.ptr = buf; + return 0; } /*