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>

1 files changed, 315 insertions, 0 deletions

diff --git a/sound/core/seq_device.c b/sound/core/seq_device.c
new file mode 100644
index 000000000000..c4acf17e9f5e
--- /dev/null
+++ b/sound/core/seq_device.c
@@ -0,0 +1,315 @@
+/*
+ *  ALSA sequencer device management
+ *  Copyright (c) 1999 by Takashi Iwai <tiwai@suse.de>
+ *
+ *   This program is free software; you can redistribute it and/or modify
+ *   it under the terms of the GNU General Public License as published by
+ *   the Free Software Foundation; either version 2 of the License, or
+ *   (at your option) any later version.
+ *
+ *   This program is distributed in the hope that it will be useful,
+ *   but WITHOUT ANY WARRANTY; without even the implied warranty of
+ *   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ *   GNU General Public License for more details.
+ *
+ *   You should have received a copy of the GNU General Public License
+ *   along with this program; if not, write to the Free Software
+ *   Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307 USA
+ *
+ *
+ *----------------------------------------------------------------
+ *
+ * This device handler separates the card driver module from sequencer
+ * stuff (sequencer core, synth drivers, etc), so that user can avoid
+ * to spend unnecessary resources e.g. if he needs only listening to
+ * MP3s.
+ *
+ * The card (or lowlevel) driver creates a sequencer device entry
+ * via snd_seq_device_new().  This is an entry pointer to communicate
+ * with the sequencer device "driver", which is involved with the
+ * actual part to communicate with the sequencer core.
+ * Each sequencer device entry has an id string and the corresponding
+ * driver with the same id is loaded when required.  For example,
+ * lowlevel codes to access emu8000 chip on sbawe card are included in
+ * emu8000-synth module.  To activate this module, the hardware
+ * resources like i/o port are passed via snd_seq_device argument.
+ *
+ */
+
+#include <linux/device.h>
+#include <linux/init.h>
+#include <linux/module.h>
+#include <sound/core.h>
+#include <sound/info.h>
+#include <sound/seq_device.h>
+#include <sound/seq_kernel.h>
+#include <sound/initval.h>
+#include <linux/kmod.h>
+#include <linux/slab.h>
+#include <linux/mutex.h>
+
+MODULE_AUTHOR("Takashi Iwai <tiwai@suse.de>");
+MODULE_DESCRIPTION("ALSA sequencer device management");
+MODULE_LICENSE("GPL");
+
+/*
+ * bus definition
+ */
+static int snd_seq_bus_match(struct device *dev, struct device_driver *drv)
+{
+	struct snd_seq_device *sdev = to_seq_dev(dev);
+	struct snd_seq_driver *sdrv = to_seq_drv(drv);
+
+	return strcmp(sdrv->id, sdev->id) == 0 &&
+		sdrv->argsize == sdev->argsize;
+}
+
+static struct bus_type snd_seq_bus_type = {
+	.name = "snd_seq",
+	.match = snd_seq_bus_match,
+};
+
+/*
+ * proc interface -- just for compatibility
+ */
+#ifdef CONFIG_SND_PROC_FS
+static struct snd_info_entry *info_entry;
+
+static int print_dev_info(struct device *dev, void *data)
+{
+	struct snd_seq_device *sdev = to_seq_dev(dev);
+	struct snd_info_buffer *buffer = data;
+
+	snd_iprintf(buffer, "snd-%s,%s,%d\n", sdev->id,
+		    dev->driver ? "loaded" : "empty",
+		    dev->driver ? 1 : 0);
+	return 0;
+}
+
+static void snd_seq_device_info(struct snd_info_entry *entry,
+				struct snd_info_buffer *buffer)
+{
+	bus_for_each_dev(&snd_seq_bus_type, NULL, buffer, print_dev_info);
+}
+#endif
+
+/*
+ * load all registered drivers (called from seq_clientmgr.c)
+ */
+
+#ifdef CONFIG_MODULES
+/* flag to block auto-loading */
+static atomic_t snd_seq_in_init = ATOMIC_INIT(1); /* blocked as default */
+
+static int request_seq_drv(struct device *dev, void *data)
+{
+	struct snd_seq_device *sdev = to_seq_dev(dev);
+
+	if (!dev->driver)
+		request_module("snd-%s", sdev->id);
+	return 0;
+}
+
+static void autoload_drivers(struct work_struct *work)
+{
+	/* avoid reentrance */
+	if (atomic_inc_return(&snd_seq_in_init) == 1)
+		bus_for_each_dev(&snd_seq_bus_type, NULL, NULL,
+				 request_seq_drv);
+	atomic_dec(&snd_seq_in_init);
+}
+
+static DECLARE_WORK(autoload_work, autoload_drivers);
+
+static void queue_autoload_drivers(void)
+{
+	schedule_work(&autoload_work);
+}
+
+void snd_seq_autoload_init(void)
+{
+	atomic_dec(&snd_seq_in_init);
+#ifdef CONFIG_SND_SEQUENCER_MODULE
+	/* initial autoload only when snd-seq is a module */
+	queue_autoload_drivers();
+#endif
+}
+EXPORT_SYMBOL(snd_seq_autoload_init);
+
+void snd_seq_autoload_exit(void)
+{
+	atomic_inc(&snd_seq_in_init);
+}
+EXPORT_SYMBOL(snd_seq_autoload_exit);
+
+void snd_seq_device_load_drivers(void)
+{
+	queue_autoload_drivers();
+	flush_work(&autoload_work);
+}
+EXPORT_SYMBOL(snd_seq_device_load_drivers);
+#else
+#define queue_autoload_drivers() /* NOP */
+#endif
+
+/*
+ * device management
+ */
+static int snd_seq_device_dev_free(struct snd_device *device)
+{
+	struct snd_seq_device *dev = device->device_data;
+
+	put_device(&dev->dev);
+	return 0;
+}
+
+static int snd_seq_device_dev_register(struct snd_device *device)
+{
+	struct snd_seq_device *dev = device->device_data;
+	int err;
+
+	err = device_add(&dev->dev);
+	if (err < 0)
+		return err;
+	if (!dev->dev.driver)
+		queue_autoload_drivers();
+	return 0;
+}
+
+static int snd_seq_device_dev_disconnect(struct snd_device *device)
+{
+	struct snd_seq_device *dev = device->device_data;
+
+	device_del(&dev->dev);
+	return 0;
+}
+
+static void snd_seq_dev_release(struct device *dev)
+{
+	struct snd_seq_device *sdev = to_seq_dev(dev);
+
+	if (sdev->private_free)
+		sdev->private_free(sdev);
+	kfree(sdev);
+}
+
+/*
+ * register a sequencer device
+ * card = card info
+ * device = device number (if any)
+ * id = id of driver
+ * result = return pointer (NULL allowed if unnecessary)
+ */
+int snd_seq_device_new(struct snd_card *card, int device, const char *id,
+		       int argsize, struct snd_seq_device **result)
+{
+	struct snd_seq_device *dev;
+	int err;
+	static struct snd_device_ops dops = {
+		.dev_free = snd_seq_device_dev_free,
+		.dev_register = snd_seq_device_dev_register,
+		.dev_disconnect = snd_seq_device_dev_disconnect,
+	};
+
+	if (result)
+		*result = NULL;
+
+	if (snd_BUG_ON(!id))
+		return -EINVAL;
+
+	dev = kzalloc(sizeof(*dev) + argsize, GFP_KERNEL);
+	if (!dev)
+		return -ENOMEM;
+
+	/* set up device info */
+	dev->card = card;
+	dev->device = device;
+	dev->id = id;
+	dev->argsize = argsize;
+
+	device_initialize(&dev->dev);
+	dev->dev.parent = &card->card_dev;
+	dev->dev.bus = &snd_seq_bus_type;
+	dev->dev.release = snd_seq_dev_release;
+	dev_set_name(&dev->dev, "%s-%d-%d", dev->id, card->number, device);
+
+	/* add this device to the list */
+	err = snd_device_new(card, SNDRV_DEV_SEQUENCER, dev, &dops);
+	if (err < 0) {
+		put_device(&dev->dev);
+		return err;
+	}
+	
+	if (result)
+		*result = dev;
+
+	return 0;
+}
+EXPORT_SYMBOL(snd_seq_device_new);
+
+/*
+ * driver registration
+ */
+int __snd_seq_driver_register(struct snd_seq_driver *drv, struct module *mod)
+{
+	if (WARN_ON(!drv->driver.name || !drv->id))
+		return -EINVAL;
+	drv->driver.bus = &snd_seq_bus_type;
+	drv->driver.owner = mod;
+	return driver_register(&drv->driver);
+}
+EXPORT_SYMBOL_GPL(__snd_seq_driver_register);
+
+void snd_seq_driver_unregister(struct snd_seq_driver *drv)
+{
+	driver_unregister(&drv->driver);
+}
+EXPORT_SYMBOL_GPL(snd_seq_driver_unregister);
+
+/*
+ * module part
+ */
+
+static int __init seq_dev_proc_init(void)
+{
+#ifdef CONFIG_SND_PROC_FS
+	info_entry = snd_info_create_module_entry(THIS_MODULE, "drivers",
+						  snd_seq_root);
+	if (info_entry == NULL)
+		return -ENOMEM;
+	info_entry->content = SNDRV_INFO_CONTENT_TEXT;
+	info_entry->c.text.read = snd_seq_device_info;
+	if (snd_info_register(info_entry) < 0) {
+		snd_info_free_entry(info_entry);
+		return -ENOMEM;
+	}
+#endif
+	return 0;
+}
+
+static int __init alsa_seq_device_init(void)
+{
+	int err;
+
+	err = bus_register(&snd_seq_bus_type);
+	if (err < 0)
+		return err;
+	err = seq_dev_proc_init();
+	if (err < 0)
+		bus_unregister(&snd_seq_bus_type);
+	return err;
+}
+
+static void __exit alsa_seq_device_exit(void)
+{
+#ifdef CONFIG_MODULES
+	cancel_work_sync(&autoload_work);
+#endif
+#ifdef CONFIG_SND_PROC_FS
+	snd_info_free_entry(info_entry);
+#endif
+	bus_unregister(&snd_seq_bus_type);
+}
+
+subsys_initcall(alsa_seq_device_init)
+module_exit(alsa_seq_device_exit)