ALSA: rawmidi: introduce SNDRV_RAWMIDI_IOCTL_USER_PVERSION

The new framing mode causes the user space regression, because
the alsa-lib code does not initialize the reserved space in
the params structure when the device is opened.

This change adds SNDRV_RAWMIDI_IOCTL_USER_PVERSION like we
do for the PCM interface for the protocol acknowledgment.

Cc: David Henningsson <coding@diwic.se>
Cc: <stable@vger.kernel.org>
Fixes: 08fdced60c ("ALSA: rawmidi: Add framing mode")
BugLink: https://github.com/alsa-project/alsa-lib/issues/178
Signed-off-by: Jaroslav Kysela <perex@perex.cz>
Link: https://lore.kernel.org/r/20210920171850.154186-1-perex@perex.cz
Signed-off-by: Takashi Iwai <tiwai@suse.de>

include/sound/rawmidi.h

@@ -98,6 +98,7 @@ struct snd_rawmidi_file {
 	struct snd_rawmidi *rmidi;
 	struct snd_rawmidi_substream *input;
 	struct snd_rawmidi_substream *output;
+	unsigned int user_pversion;	/* supported protocol version */
 };
 
 struct snd_rawmidi_str {

include/uapi/sound/asound.h

@@ -784,6 +784,7 @@ struct snd_rawmidi_status {
 
 #define SNDRV_RAWMIDI_IOCTL_PVERSION	_IOR('W', 0x00, int)
 #define SNDRV_RAWMIDI_IOCTL_INFO	_IOR('W', 0x01, struct snd_rawmidi_info)
+#define SNDRV_RAWMIDI_IOCTL_USER_PVERSION _IOW('W', 0x02, int)
 #define SNDRV_RAWMIDI_IOCTL_PARAMS	_IOWR('W', 0x10, struct snd_rawmidi_params)
 #define SNDRV_RAWMIDI_IOCTL_STATUS	_IOWR('W', 0x20, struct snd_rawmidi_status)
 #define SNDRV_RAWMIDI_IOCTL_DROP	_IOW('W', 0x30, int)

sound/core/rawmidi.c

@@ -873,12 +873,21 @@ static long snd_rawmidi_ioctl(struct file *file, unsigned int cmd, unsigned long
 			return -EINVAL;
 		}
 	}
+	case SNDRV_RAWMIDI_IOCTL_USER_PVERSION:
+		if (get_user(rfile->user_pversion, (unsigned int __user *)arg))
+			return -EFAULT;
+		return 0;
+
 	case SNDRV_RAWMIDI_IOCTL_PARAMS:
 	{
 		struct snd_rawmidi_params params;
 
 		if (copy_from_user(&params, argp, sizeof(struct snd_rawmidi_params)))
 			return -EFAULT;
+		if (rfile->user_pversion < SNDRV_PROTOCOL_VERSION(2, 0, 2)) {
+			params.mode = 0;
+			memset(params.reserved, 0, sizeof(params.reserved));
+		}
 		switch (params.stream) {
 		case SNDRV_RAWMIDI_STREAM_OUTPUT:
 			if (rfile->output == NULL)