greybus: audio: Add Audio Manager

This is a simple module that keeps a list of connected GB audio
modules.

Whenever a device is attached, an appropriate uevent is sent to
userspace:

    UDEV  [4941.803215] add      /kernel/gb_audio_manager/0 (gb_audio_manager)
    ACTION=add
    CPORT=99
    DEVICES=0x10
    DEVPATH=/kernel/gb_audio_manager/0
    NAME=naim
    PID=64
    SEQNUM=1828
    SLOT=2
    SUBSYSTEM=gb_audio_manager
    USEC_INITIALIZED=802416
    VID=128

And whenever removed:

    UDEV  [4941.836588] remove   /kernel/gb_audio_manager/0 (gb_audio_manager)
    ACTION=remove
    DEVPATH=/kernel/gb_audio_manager/0
    SEQNUM=1833
    SUBSYSTEM=gb_audio_manager
    USEC_INITIALIZED=835681

The API consists of functions for adding, removing and inspecting
added device module descriptions (struct gb_audio_module):

    int                         gb_audio_manager_add(struct gb_audio_module_descriptor *desc);
    int                         gb_audio_manager_remove(int id);
    int                         gb_audio_manager_remove_all(void);
    struct  gb_audio_module*    gb_audio_manager_get_module(int id);
    void                        gb_audio_manager_put_module(struct gb_audio_module *module);
    int                         gb_audio_manager_dump_module(int id);
    void                        gb_audio_manager_dump_all(void);

Devices can be inspected through sysfs in /sys/kernel/gb_audio_manager/{id}/*

If GB_AUDIO_MANAGER_SYSFS is exported as 'true', managing devices can be done
via the SYSFS as well. For instance:

    echo name=naim slot=2 vid=128 pid=64 cport=99 devices=0x10 > /sys/kernel/gb_audio_manager/add
    echo all > /sys/kernel/gb_audio_manager/dump
    echo 2 > /sys/kernel/gb_audio_manager/dump
    echo 2 > /sys/kernel/gb_audio_manager/remove

Signed-off-by: Svetlin Ankov <ankov_svetlin@projectara.com>
Signed-off-by: Mark Greer <mgreer@animalcreek.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@google.com>

1 files changed, 184 insertions, 0 deletions

diff --git a/drivers/staging/greybus/audio_manager.c b/drivers/staging/greybus/audio_manager.c
new file mode 100644
index 000000000000..117676314daf
--- /dev/null
+++ b/drivers/staging/greybus/audio_manager.c
@@ -0,0 +1,184 @@
+/*
+ * Greybus operations
+ *
+ * Copyright 2015-2016 Google Inc.
+ *
+ * Released under the GPLv2 only.
+ */
+
+#include <linux/string.h>
+#include <linux/sysfs.h>
+#include <linux/module.h>
+#include <linux/init.h>
+#include <linux/rwlock.h>
+
+#include "audio_manager.h"
+#include "audio_manager_private.h"
+
+static struct kset *manager_kset;
+
+static LIST_HEAD(modules_list);
+static DEFINE_RWLOCK(modules_lock);
+
+static int current_module_id;
+
+/* helpers */
+static struct gb_audio_manager_module *gb_audio_manager_get_locked(int id)
+{
+	struct gb_audio_manager_module *module;
+
+	if (id < 0)
+		return NULL;
+
+	list_for_each_entry(module, &modules_list, list) {
+		if (module->id == id)
+			return module;
+	}
+
+	return NULL;
+}
+
+/* public API */
+int gb_audio_manager_add(struct gb_audio_manager_module_descriptor *desc)
+{
+	struct gb_audio_manager_module *module;
+	unsigned long flags;
+	int err;
+
+	err = gb_audio_manager_module_create(&module, manager_kset,
+					     current_module_id++, desc);
+	if (err)
+		return err;
+
+	/* Add it to the list */
+	write_lock_irqsave(&modules_lock, flags);
+	list_add_tail(&module->list, &modules_list);
+	write_unlock_irqrestore(&modules_lock, flags);
+
+	return module->id;
+}
+EXPORT_SYMBOL_GPL(gb_audio_manager_add);
+
+int gb_audio_manager_remove(int id)
+{
+	struct gb_audio_manager_module *module;
+	unsigned long flags;
+
+	write_lock_irqsave(&modules_lock, flags);
+
+	module = gb_audio_manager_get_locked(id);
+	if (!module) {
+		write_unlock_irqrestore(&modules_lock, flags);
+		return -EINVAL;
+	}
+
+	list_del(&module->list);
+	kobject_put(&module->kobj);
+	write_unlock_irqrestore(&modules_lock, flags);
+	return 0;
+}
+EXPORT_SYMBOL_GPL(gb_audio_manager_remove);
+
+void gb_audio_manager_remove_all(void)
+{
+	struct gb_audio_manager_module *module, *next;
+	int is_empty = 1;
+	unsigned long flags;
+
+	write_lock_irqsave(&modules_lock, flags);
+
+	list_for_each_entry_safe(module, next, &modules_list, list) {
+		list_del(&module->list);
+		kobject_put(&module->kobj);
+	}
+
+	is_empty = list_empty(&modules_list);
+
+	write_unlock_irqrestore(&modules_lock, flags);
+
+	if (!is_empty)
+		pr_warn("Not all nodes were deleted\n");
+}
+EXPORT_SYMBOL_GPL(gb_audio_manager_remove_all);
+
+struct gb_audio_manager_module *gb_audio_manager_get_module(int id)
+{
+	struct gb_audio_manager_module *module;
+	unsigned long flags;
+
+	read_lock_irqsave(&modules_lock, flags);
+	module = gb_audio_manager_get_locked(id);
+	kobject_get(&module->kobj);
+	read_unlock_irqrestore(&modules_lock, flags);
+	return module;
+}
+EXPORT_SYMBOL_GPL(gb_audio_manager_get_module);
+
+void gb_audio_manager_put_module(struct gb_audio_manager_module *module)
+{
+	kobject_put(&module->kobj);
+}
+EXPORT_SYMBOL_GPL(gb_audio_manager_put_module);
+
+int gb_audio_manager_dump_module(int id)
+{
+	struct gb_audio_manager_module *module;
+	unsigned long flags;
+
+	read_lock_irqsave(&modules_lock, flags);
+	module = gb_audio_manager_get_locked(id);
+	read_unlock_irqrestore(&modules_lock, flags);
+
+	if (!module)
+		return -EINVAL;
+
+	gb_audio_manager_module_dump(module);
+	return 0;
+}
+EXPORT_SYMBOL_GPL(gb_audio_manager_dump_module);
+
+void gb_audio_manager_dump_all(void)
+{
+	struct gb_audio_manager_module *module;
+	int count = 0;
+	unsigned long flags;
+
+	read_lock_irqsave(&modules_lock, flags);
+	list_for_each_entry(module, &modules_list, list) {
+		gb_audio_manager_module_dump(module);
+		count++;
+	}
+	read_unlock_irqrestore(&modules_lock, flags);
+
+	pr_info("Number of connected modules: %d\n", count);
+}
+EXPORT_SYMBOL_GPL(gb_audio_manager_dump_all);
+
+/*
+ * module init/deinit
+ */
+static int __init manager_init(void)
+{
+	manager_kset = kset_create_and_add(GB_AUDIO_MANAGER_NAME, NULL,
+					   kernel_kobj);
+	if (!manager_kset)
+		return -ENOMEM;
+
+#ifdef GB_AUDIO_MANAGER_SYSFS
+	gb_audio_manager_sysfs_init(&manager_kset->kobj);
+#endif
+
+	return 0;
+}
+
+static void __exit manager_exit(void)
+{
+	gb_audio_manager_remove_all();
+	kset_unregister(manager_kset);
+}
+
+module_init(manager_init);
+module_exit(manager_exit);
+
+MODULE_LICENSE("GPL");
+MODULE_AUTHOR("Svetlin Ankov <ankov_svetlin@projectara.com>");