ALSA: seq: Allow the modular sequencer registration

Many drivers bind the sequencer stuff in off-load by another driver
module, so that it's loaded only on demand.  In the current code, this
mechanism doesn't work when the driver is built-in while the sequencer
is module.  We check with IS_REACHABLE() and enable only when the
sequencer is in the same level of build.

However, this is basically a overshoot.  The binder code
(snd-seq-device) is an individual module from the sequencer core
(snd-seq), and we just have to make the former a built-in while
keeping the latter a module for allowing the scenario like the above.

This patch achieves that by rewriting Kconfig slightly.  Now, a driver
that provides the manual sequencer device binding should select
CONFIG_SND_SEQ_DEVICE in a way as
	select SND_SEQ_DEVICE if SND_SEQUENCER != n

Note that the "!=n" is needed here to avoid the influence of the
sequencer core is module while the driver is built-in.

Also, since rawmidi.o may be linked with snd_seq_device.o when
built-in, we have to shuffle the code to make the linker happy.
(the kernel linker isn't smart enough yet to handle such a case.)
That is, snd_seq_device.c is moved to sound/core from sound/core/seq,
as well as Makefile.

Last but not least, the patch replaces the code using IS_REACHABLE()
with IS_ENABLED(), since now the condition meets always when enabled.

Signed-off-by: Takashi Iwai <tiwai@suse.de>

2 files changed, 3 insertions, 3 deletions

diff --git a/sound/drivers/opl4/opl4_lib.c b/sound/drivers/opl4/opl4_lib.c
index 240656e54400..bc345d564f8d 100644
--- a/sound/drivers/opl4/opl4_lib.c
+++ b/sound/drivers/opl4/opl4_lib.c
@@ -153,7 +153,7 @@ static int snd_opl4_detect(struct snd_opl4 *opl4)
 	return 0;
 }
 
-#if IS_REACHABLE(CONFIG_SND_SEQUENCER)
+#if IS_ENABLED(CONFIG_SND_SEQUENCER)
 static void snd_opl4_seq_dev_free(struct snd_seq_device *seq_dev)
 {
 	struct snd_opl4 *opl4 = seq_dev->private_data;
@@ -249,7 +249,7 @@ int snd_opl4_create(struct snd_card *card,
 	snd_opl4_create_mixer(opl4);
 	snd_opl4_create_proc(opl4);
 
-#if IS_REACHABLE(CONFIG_SND_SEQUENCER)
+#if IS_ENABLED(CONFIG_SND_SEQUENCER)
 	opl4->seq_client = -1;
 	if (opl4->hardware < OPL3_HW_OPL4_ML)
 		snd_opl4_create_seq_dev(opl4, seq_device);
diff --git a/sound/drivers/opl4/opl4_local.h b/sound/drivers/opl4/opl4_local.h
index d5bac93f8245..a16b4677c1e9 100644
--- a/sound/drivers/opl4/opl4_local.h
+++ b/sound/drivers/opl4/opl4_local.h
@@ -184,7 +184,7 @@ struct snd_opl4 {
 #endif
 	struct mutex access_mutex;
 
-#if IS_REACHABLE(CONFIG_SND_SEQUENCER)
+#if IS_ENABLED(CONFIG_SND_SEQUENCER)
 	int used;
 
 	int seq_dev_num;