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ALSA: ump: Add helper to change MIDI protocol

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This is a preliminary patch for MIDI 2.0 USB gadget driver.
Export a new helper to allow changing the current MIDI protocol from
the outside.

Link: https://lore.kernel.org/r/20230621110241.4751-2-tiwai@suse.de
Signed-off-by: Takashi Iwai <tiwai@suse.de>
This commit is contained in:
Takashi Iwai 2023-06-21 13:02:39 +02:00
parent febdfa0e9c
commit a798076837
2 changed files with 26 additions and 7 deletions
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2
include/sound/ump.h
View File

@ -108,6 +108,8 @@ static inline int snd_ump_attach_legacy_rawmidi(struct snd_ump_endpoint *ump,
}
#endif
int snd_ump_switch_protocol(struct snd_ump_endpoint *ump, unsigned int protocol);
/*
* Some definitions for UMP
*/

31
sound/core/ump.c
View File

@ -671,18 +671,35 @@ static void seq_notify_protocol(struct snd_ump_endpoint *ump)
#endif /* CONFIG_SND_SEQUENCER */
}
/**
* snd_ump_switch_protocol - switch MIDI protocol
* @ump: UMP endpoint
* @protocol: protocol to switch to
*
* Returns 1 if the protocol is actually switched, 0 if unchanged
*/
int snd_ump_switch_protocol(struct snd_ump_endpoint *ump, unsigned int protocol)
{
protocol &= ump->info.protocol_caps;
if (protocol == ump->info.protocol)
return 0;
ump->info.protocol = protocol;
ump_dbg(ump, "New protocol = %x (caps = %x)\n",
protocol, ump->info.protocol_caps);
seq_notify_protocol(ump);
return 1;
}
EXPORT_SYMBOL_GPL(snd_ump_switch_protocol);
/* handle EP stream config message; update the UMP protocol */
static int ump_handle_stream_cfg_msg(struct snd_ump_endpoint *ump,
const union snd_ump_stream_msg *buf)
{
unsigned int old_protocol = ump->info.protocol;
ump->info.protocol =
unsigned int protocol =
(buf->stream_cfg.protocol << 8) | buf->stream_cfg.jrts;
ump_dbg(ump, "Current protocol = %x (caps = %x)\n",
ump->info.protocol, ump->info.protocol_caps);
if (ump->parsed && ump->info.protocol != old_protocol)
seq_notify_protocol(ump);
snd_ump_switch_protocol(ump, protocol);
return 1; /* finished */
}