[PATCHv3 1/4] modem_shm: Add Modem Access Framework

[Arun Murthy]

Adds Modem Access Framework, which allows for registering platform specific
modem access mechanisms. The framework also exposes APIs for client drivers
for getting and releasing access to modem, regardless of the underlying
platform specific access mechanism.

Signed-off-by: Arun Murthy <arun.murthy@xxxxxxxxxxxxxx>
---
 drivers/Kconfig                        |    2 +
 drivers/Makefile                       |    1 +
 drivers/modem_shm/Kconfig              |    9 +
 drivers/modem_shm/Makefile             |    1 +
 drivers/modem_shm/modem_access.c       |  413 ++++++++++++++++++++++++++++++++
 include/linux/modem_shm/modem.h        |   64 +++++
 include/linux/modem_shm/modem_client.h |   55 +++++
 7 files changed, 545 insertions(+), 0 deletions(-)
 create mode 100644 drivers/modem_shm/Kconfig
 create mode 100644 drivers/modem_shm/Makefile
 create mode 100644 drivers/modem_shm/modem_access.c
 create mode 100644 include/linux/modem_shm/modem.h
 create mode 100644 include/linux/modem_shm/modem_client.h

diff --git a/drivers/Kconfig b/drivers/Kconfig
index ece958d..dc7c14a 100644
--- a/drivers/Kconfig
+++ b/drivers/Kconfig
@@ -152,4 +152,6 @@ source "drivers/vme/Kconfig"
 
 source "drivers/pwm/Kconfig"
 
+source "drivers/modem_shm/Kconfig"
+
 endmenu
diff --git a/drivers/Makefile b/drivers/Makefile
index 5b42184..902dfec 100644
--- a/drivers/Makefile
+++ b/drivers/Makefile
@@ -139,3 +139,4 @@ obj-$(CONFIG_EXTCON)		+= extcon/
 obj-$(CONFIG_MEMORY)		+= memory/
 obj-$(CONFIG_IIO)		+= iio/
 obj-$(CONFIG_VME_BUS)		+= vme/
+obj-$(CONFIG_MODEM_SHM)		+= modem_shm/
diff --git a/drivers/modem_shm/Kconfig b/drivers/modem_shm/Kconfig
new file mode 100644
index 0000000..f4b7e54
--- /dev/null
+++ b/drivers/modem_shm/Kconfig
@@ -0,0 +1,9 @@
+config MODEM_SHM
+        bool "Modem Access Framework"
+        default n
+        help
+         Add support for Modem Access Framework. It allows different
+	 platform specific drivers to register modem access mechanisms
+	 and allows transparent access to modem to the client drivers.
+
+	 If unsure, say N.
diff --git a/drivers/modem_shm/Makefile b/drivers/modem_shm/Makefile
new file mode 100644
index 0000000..b77bcc0
--- /dev/null
+++ b/drivers/modem_shm/Makefile
@@ -0,0 +1 @@
+obj-$(CONFIG_MODEM_SHM)		:= modem_access.o
diff --git a/drivers/modem_shm/modem_access.c b/drivers/modem_shm/modem_access.c
new file mode 100644
index 0000000..b4bb4b7
--- /dev/null
+++ b/drivers/modem_shm/modem_access.c
@@ -0,0 +1,413 @@
+/*
+ * Copyright (C) ST-Ericsson SA 2011
+ *
+ * License Terms: GNU General Public License v2
+ * Author: Kumar Sanghvi
+ *	Arun Murthy <arun.murthy@xxxxxxxxxxxxxx>
+ *
+ * Heavily adapted from Regulator framework.
+ * Provides mechanisms for registering platform specific access
+ * mechanisms for modem.
+ * Also, exposes APIs for gettng/releasing the access and even
+ * query the access status, and the modem usage status.
+ */
+#include <linux/module.h>
+#include <linux/modem_shm/modem.h>
+#include <linux/modem_shm/modem_client.h>
+#include <linux/slab.h>
+#include <linux/err.h>
+
+static DEFINE_MUTEX(modem_list_mutex);
+static LIST_HEAD(modem_list);
+
+struct modem {
+	struct device *dev;
+	struct list_head list;
+	char *modem_name;
+	struct device_attribute dev_attr;
+	struct modem_dev *mdev;
+	atomic_t use;
+};
+
+static enum mod_state {
+	MOD_RELEASED,
+	MOD_ACCESSED,
+};
+
+static const char *mdev_get_name(struct modem_dev *mdev)
+{
+	if (mdev->desc->name)
+		return mdev->desc->name;
+	else
+		return "";
+}
+
+static int _modem_is_requested(struct modem_dev *mdev)
+{
+	/* If we don't know then assume that the modem is always on */
+	if (!mdev->desc->ops->is_requested)
+		return 0;
+
+	return mdev->desc->ops->is_requested(mdev);
+}
+
+/**
+ * modem_is_requested - check if modem access is requested
+ * @modem: modem device
+ *
+ * Checks whether modem is accessed or not by querying
+ * the underlying platform specific modem access
+ * implementation.
+ */
+int modem_is_requested(struct modem *modem)
+{
+	int ret;
+
+	mutex_lock(&modem->mdev->mutex);
+	ret = _modem_is_requested(modem->mdev);
+	mutex_unlock(&modem->mdev->mutex);
+
+	return ret;
+}
+EXPORT_SYMBOL_GPL(modem_is_requested);
+
+static int _modem_request(struct modem_dev *mdev)
+{
+	int ret;
+
+	if (++mdev->use_count == 1) {
+		ret = _modem_is_requested(mdev);
+		if (ret == 0)
+			mdev->desc->ops->request(mdev);
+	}
+
+	return 0;
+}
+
+/**
+ * modem_request - Request access the modem
+ * @modem: modem device
+ *
+ * API to access the modem. It keeps a client
+ * specific check on whether the particular modem
+ * requested is accessed or not.
+ */
+int modem_request(struct modem *modem)
+{
+	struct modem_dev *mdev = modem->mdev;
+	int ret = 0;
+
+
+	mutex_lock(&mdev->mutex);
+	if (atomic_read(&modem->use) == 1) {
+		mutex_unlock(&mdev->mutex);
+		return ret;
+	}
+	ret = _modem_request(mdev);
+	if (ret == 0)
+		atomic_set(&modem->use, 1);
+	mutex_unlock(&mdev->mutex);
+	return ret;
+}
+EXPORT_SYMBOL_GPL(modem_request);
+
+static int _modem_release(struct modem_dev *mdev)
+{
+	if (WARN(mdev->use_count <= 0,
+				"unbalanced releases for %s\n",
+				mdev_get_name(mdev)))
+		return -EIO;
+
+	if (--mdev->use_count == 0)
+		mdev->desc->ops->release(mdev);
+
+	return 0;
+}
+
+/**
+ * modem_release - Release access to modem
+ * @modem: modem device
+ *
+ * Releases accesss to the modem. It keeps a client
+ * specific check on whether a particular modem
+ * is released or not.
+ */
+void modem_release(struct modem *modem)
+{
+	struct modem_dev *mdev = modem->mdev;
+	int ret = 0;
+
+	mutex_lock(&mdev->mutex);
+	if (atomic_read(&modem->use) == 0) {
+		mutex_unlock(&mdev->mutex);
+		return;
+	}
+	ret = _modem_release(mdev);
+	if (ret == 0)
+		atomic_set(&modem->use, 0);
+	mutex_unlock(&mdev->mutex);
+}
+EXPORT_SYMBOL_GPL(modem_release);
+
+/**
+ * modem_get_usage - Check if particular client is using modem
+ * @modem: modem device
+ *
+ * Checks whether the particular client is using access to modem.
+ * This API could be used by client drivers in making their
+ * suspend decisions.
+ */
+int modem_get_usage(struct modem *modem)
+{
+	return atomic_read(&modem->use);
+}
+EXPORT_SYMBOL_GPL(modem_get_usage);
+
+static struct modem *create_modem(struct modem_dev *mdev,
+		struct device *dev,
+		const char *id)
+{
+	struct modem *modem;
+
+	modem = kzalloc(sizeof(*modem), GFP_KERNEL);
+	if (modem == NULL)
+		return NULL;
+
+	mutex_lock(&mdev->mutex);
+	modem->mdev = mdev;
+	modem->dev = dev;
+	list_add(&modem->list, &mdev->client_list);
+
+	mutex_unlock(&mdev->mutex);
+	return modem;
+
+}
+
+static struct modem *_modem_get(struct device *dev, const char *id,
+		int exclusive)
+{
+	struct modem_dev *mdev_ptr;
+	struct modem *modem = ERR_PTR(-ENODEV);
+	int ret;
+
+	if (id == NULL) {
+		pr_err("modem_get with no identifier\n");
+		return modem;
+	}
+
+	mutex_lock(&modem_list_mutex);
+	list_for_each_entry(mdev_ptr, &modem_list, modem_list) {
+		if (strcmp(mdev_get_name(mdev_ptr), id) == 0)
+			goto found;
+	}
+
+	goto out;
+
+found:
+	if (!try_module_get(mdev_ptr->owner))
+		goto out;
+
+	modem = create_modem(mdev_ptr, dev, id);
+	if (modem == NULL) {
+		modem = ERR_PTR(-ENOMEM);
+		module_put(mdev_ptr->owner);
+	}
+
+	mdev_ptr->open_count++;
+	ret = _modem_is_requested(mdev_ptr);
+	if (ret)
+		mdev_ptr->use_count = 1;
+	else
+		mdev_ptr->use_count = 0;
+
+out:
+	mutex_unlock(&modem_list_mutex);
+	return modem;
+
+}
+
+/**
+ * modem_get - Get reference to a particular platform specific modem
+ * @dev: device
+ * @id: modem device name
+ *
+ * Get reference to a particular modem device.
+ */
+struct modem *modem_get(struct device *dev, const char *id)
+{
+	return _modem_get(dev, id, 0);
+}
+EXPORT_SYMBOL_GPL(modem_get);
+
+/**
+ * modem_put - Release reference to a modem device
+ * @modem: modem device
+ *
+ * Release reference to a modem device.
+ */
+void modem_put(struct modem *modem)
+{
+	struct modem_dev *mdev;
+
+	if (modem == NULL || IS_ERR(modem))
+		return;
+
+	mutex_lock(&modem_list_mutex);
+	mdev = modem->mdev;
+
+	list_del(&modem->list);
+	kfree(modem);
+
+	mdev->open_count--;
+
+	module_put(mdev->owner);
+	mutex_unlock(&modem_list_mutex);
+}
+EXPORT_SYMBOL_GPL(modem_put);
+
+static ssize_t modem_print_state(char *buf, int state)
+{
+	if (state > MOD_ACCESSED)
+		return sprintf(buf, "accessed\n");
+	else if (state == MOD_RELEASED)
+		return sprintf(buf, "released\n");
+	else
+		return sprintf(buf, "unknown\n");
+}
+
+static ssize_t modem_state_show(struct device *dev,
+		struct device_attribute *attr, char *buf)
+{
+	struct modem_dev *mdev = dev_get_drvdata(dev);
+	ssize_t ret;
+
+	mutex_lock(&mdev->mutex);
+	ret = modem_print_state(buf, _modem_is_requested(mdev));
+	mutex_unlock(&mdev->mutex);
+
+	return ret;
+}
+static DEVICE_ATTR(state, (S_IWUSR | S_IRGRP | S_IROTH),
+		modem_state_show, NULL);
+
+static ssize_t modem_use_show(struct device *dev,
+		struct device_attribute *attr, char *buf)
+{
+	struct modem_dev *mdev = dev_get_drvdata(dev);
+	struct modem *mod;
+	size_t size = 0;
+
+	list_for_each_entry(mod, &mdev->client_list, list) {
+		if (mod->dev != NULL)
+			size += sprintf((buf + size), "%s (%d)\n",
+				dev_name(mod->dev), atomic_read(&mod->use));
+		else
+			size += sprintf((buf + size), "unknown (%d)\n",
+				atomic_read(&mod->use));
+	}
+	size += sprintf((buf + size), "\n");
+
+	return size;
+}
+static DEVICE_ATTR(use, (S_IWUSR | S_IRGRP | S_IROTH), modem_use_show, NULL);
+
+static ssize_t modem_num_active_users_show(struct device *dev,
+		struct device_attribute *attr, char *buf)
+{
+	struct modem_dev *mdev = dev_get_drvdata(dev);
+	return sprintf(buf, "%d\n", mdev->use_count);
+}
+static DEVICE_ATTR(num_active_users, (S_IWUSR | S_IRGRP | S_IROTH),
+		modem_num_active_users_show, NULL);
+
+static int add_modem_attributes(struct modem_dev *mdev)
+{
+	struct device      *dev = &mdev->dev;
+	struct modem_ops   *ops = mdev->desc->ops;
+	int                status = 0;
+
+	status = device_create_file(dev, &dev_attr_use);
+	if (status < 0)
+		return status;
+
+	status = device_create_file(dev, &dev_attr_num_active_users);
+	if (status < 0)
+		return status;
+
+	if (ops->is_requested) {
+		status = device_create_file(dev, &dev_attr_state);
+		if (status < 0)
+			return status;
+	}
+
+	return 0;
+}
+
+/**
+ * modem_register - register a modem
+ * @modem_desc: - description for modem
+ * @dev:        - device
+ * @driver_data:- driver specific data
+ *
+ * Register a modem with the modem access framework, so that
+ * it could be used by client drivers for accessing the
+ * modem.
+ */
+struct modem_dev *modem_register(struct modem_desc *modem_desc,
+		struct device *dev,
+		void *driver_data)
+{
+	static atomic_t modem_no = ATOMIC_INIT(0);
+	struct modem_dev *mdev;
+	int ret;
+
+	if (modem_desc == NULL)
+		return ERR_PTR(-EINVAL);
+
+	if (modem_desc->name == NULL || modem_desc->ops == NULL)
+		return ERR_PTR(-EINVAL);
+
+	mdev = kzalloc(sizeof(struct modem_dev), GFP_KERNEL);
+	if (mdev == NULL)
+		return ERR_PTR(-ENOMEM);
+
+	mutex_lock(&modem_list_mutex);
+
+	mutex_init(&mdev->mutex);
+	mdev->modem_data = driver_data;
+	mdev->owner = modem_desc->owner;
+	mdev->desc = modem_desc;
+	INIT_LIST_HEAD(&mdev->client_list);
+	INIT_LIST_HEAD(&mdev->modem_list);
+	BLOCKING_INIT_NOTIFIER_HEAD(&mdev->notifier);
+
+	/* mdev->dev.class = &modem_class;*/
+	mdev->dev.parent = dev;
+	dev_set_name(&mdev->dev, "modem.%d", atomic_inc_return(&modem_no) - 1);
+	ret = device_register(&mdev->dev);
+	if (ret != 0)
+		goto clean;
+
+	dev_set_drvdata(&mdev->dev, mdev);
+
+	ret = add_modem_attributes(mdev);
+	if (ret < 0)
+		goto backoff;
+
+	list_add(&mdev->modem_list, &modem_list);
+
+out:
+	mutex_unlock(&modem_list_mutex);
+	return mdev;
+
+backoff:
+	device_unregister(&mdev->dev);
+	mdev = ERR_PTR(ret);
+	goto out;
+
+clean:
+	kfree(mdev);
+	mdev = ERR_PTR(ret);
+	goto out;
+}
+EXPORT_SYMBOL_GPL(modem_register);
diff --git a/include/linux/modem_shm/modem.h b/include/linux/modem_shm/modem.h
new file mode 100644
index 0000000..aab636a
--- /dev/null
+++ b/include/linux/modem_shm/modem.h
@@ -0,0 +1,64 @@
+/*
+ * Copyright (C) ST-Ericsson SA 2011
+ *
+ * License Terms: GNU General Public License v2
+ * Author: Kumar Sanghvi
+ *	Arun Murthy <arun.murthy@xxxxxxxxxxxxxx>
+ *
+ * Heavily adapted from Regulator framework
+ */
+#ifndef __MODEM_H__
+#define __MODEM_H__
+
+#include <linux/device.h>
+
+struct modem_dev;
+
+struct modem_ops {
+	int (*request)(struct modem_dev *);
+	void (*release)(struct modem_dev *);
+	int (*is_requested)(struct modem_dev *);
+};
+
+struct modem_desc {
+	const char *name;
+	int id;
+	struct modem_ops *ops;
+	struct module *owner;
+};
+
+struct modem_dev {
+	struct modem_desc *desc;
+	int use_count;
+	int open_count;
+	int exclusive;
+
+	struct list_head modem_list;
+
+	struct list_head client_list;
+
+	struct blocking_notifier_head notifier;
+	struct mutex mutex;
+	struct module *owner;
+	struct device dev;
+	void *modem_data;
+};
+
+#ifdef CONFIG_MODEM_SHM
+struct modem_dev *modem_register(struct modem_desc *modem_desc,
+		struct device *dev,
+		void *driver_data);
+void modem_unregister(struct modem_dev *mdev);
+
+#else
+static inline struct modem_dev *modem_register(struct modem_desc *modem_desc,
+		struct device *dev, void *driver_data)
+{
+	return NULL;
+}
+
+static inline void modem_unregister(struct modem_dev *mdev)
+{
+}
+#endif
+#endif /* __MODEM_H__ */
diff --git a/include/linux/modem_shm/modem_client.h b/include/linux/modem_shm/modem_client.h
new file mode 100644
index 0000000..ad7406a
--- /dev/null
+++ b/include/linux/modem_shm/modem_client.h
@@ -0,0 +1,55 @@
+/*
+ * Copyright (C) ST-Ericsson SA 2011
+ *
+ * License Terms: GNU General Public License v2
+ * Author: Kumar Sanghvi
+ *	Arun Murthy <arun.murthy@xxxxxxxxxxxxxx>
+ *
+ * Heavily adapted from Regulator framework
+ */
+#ifndef __MODEM_CLIENT_H__
+#define __MODEM_CLIENT_H__
+
+#include <linux/device.h>
+
+struct modem;
+
+#ifdef CONFIG_MODEM_SHM
+struct modem *modem_get(struct device *dev, const char *id);
+void modem_put(struct modem *modem);
+int modem_request(struct modem *modem);
+void modem_release(struct modem *modem);
+int modem_is_requested(struct modem *modem);
+int modem_get_usage(struct modem *modem);
+
+#else
+
+static inline struct modem *modem_get(struct device *dev, const char *id)
+{
+	return NULL;
+}
+
+static inline void modem_put(struct modem *modem)
+{
+}
+
+static inline int modem_request(struct modem *modem)
+{
+	return 0;
+}
+
+static inline void modem_release(struct modem *modem)
+{
+}
+
+static inline int modem_is_requested(struct modem *modem)
+{
+	return 0;
+}
+
+static inline int modem_get_usage(struct modem *modem)
+{
+	return 0;
+}
+#endif
+#endif /* __MODEM_CLIENT_H__ */
-- 
1.7.4.3

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