Added sys_hotplug.c, which is the system device hotplug framework code.
shp_register_handler() allows modules to register their hotplug handlers
to the framework. shp_submit_req() provides the interface to submit
a hotplug or online/offline request of system devices. The request is
then put into hp_workqueue. shp_start_req() calls all registered handlers
in ascending order for each phase. If any handler failed in validate or
execute phase, shp_start_req() initiates its rollback procedure.
Signed-off-by: Toshi Kani <toshi.kani@xxxxxx>
---
drivers/base/Makefile | 1
drivers/base/sys_hotplug.c | 313 ++++++++++++++++++++++++++++++++++++++++++++
2 files changed, 314 insertions(+)
create mode 100644 drivers/base/sys_hotplug.c
diff --git a/drivers/base/Makefile b/drivers/base/Makefile
index 5aa2d70..2e9b2f1 100644
--- a/drivers/base/Makefile
+++ b/drivers/base/Makefile
@@ -21,6 +21,7 @@ endif
obj-$(CONFIG_SYS_HYPERVISOR) += hypervisor.o
obj-$(CONFIG_REGMAP) += regmap/
obj-$(CONFIG_SOC_BUS) += soc.o
+obj-y += sys_hotplug.o
ccflags-$(CONFIG_DEBUG_DRIVER) := -DDEBUG
diff --git a/drivers/base/sys_hotplug.c b/drivers/base/sys_hotplug.c
new file mode 100644
index 0000000..c5f5285
--- /dev/null
+++ b/drivers/base/sys_hotplug.c
@@ -0,0 +1,313 @@
+/*
+ * sys_hotplug.c - System device hot-plug framework
+ *
+ * Copyright (C) 2012 Hewlett-Packard Development Company, L.P.
+ * Toshi Kani <toshi.kani@xxxxxx>
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 2 as
+ * published by the Free Software Foundation.
+ */
+
+#include <linux/kernel.h>
+#include <linux/init.h>
+#include <linux/slab.h>
+#include <linux/module.h>
+#include <linux/list.h>
+#include <linux/workqueue.h>
+#include <linux/sys_hotplug.h>
+#include <linux/kallsyms.h>
+
+/*
+ * Hot-plug handler list
+ */
+struct shp_handler {
+ struct list_head shp_list;
+ int shp_order;
+ shp_func shp_func;
+};
+
+LIST_HEAD(shp_add_list_head);
+LIST_HEAD(shp_del_list_head);
+
+static DEFINE_MUTEX(shp_hdr_list_lock);
+
+#define SHP_VALIDATE_ORDER_BASE (SHP_ORDER_MAX+1)
+#define SHP_EXECUTE_ORDER_BASE ((SHP_ORDER_MAX+1) << 1)
+#define SHP_COMMIT_ORDER_BASE ((SHP_ORDER_MAX+1) << 2)
+
+/*
+ * Hot-plug request work queue
+ */
+struct shp_work {
+ struct shp_request *request;
+ struct work_struct work;
+};
+
+static struct workqueue_struct *shp_workqueue;
+
+/* trace messages */
+static int shp_trace = 1;
+static char shp_ksym_buf[KSYM_NAME_LEN];
+module_param(shp_trace, int, 0644);
+MODULE_PARM_DESC(shp_trace, "Enable system device hot-plug trace messages");
+
+static char *shp_operation_string(enum shp_operation operation)
+{
+ switch (operation) {
+ case SHP_HOTPLUG_ADD:
+ return "Hot-Add";
+ case SHP_HOTPLUG_DEL:
+ return "Hot-Delete";
+ case SHP_ONLINE_ADD:
+ return "Online";
+ case SHP_ONLINE_DEL:
+ return "Offline";
+ }
+
+ return "n/a";
+}
+
+static u32 shp_get_order_base(enum shp_phase phase)
+{
+ switch (phase) {
+ case SHP_ADD_VALIDATE:
+ case SHP_DEL_VALIDATE:
+ return SHP_VALIDATE_ORDER_BASE;
+ case SHP_ADD_EXECUTE:
+ case SHP_DEL_EXECUTE:
+ return SHP_EXECUTE_ORDER_BASE;
+ case SHP_ADD_COMMIT:
+ case SHP_DEL_COMMIT:
+ return SHP_COMMIT_ORDER_BASE;
+ }
+
+ return 0;
+}
+
+/**
+ * shp_register_handler - register a hot-plug handler to the framework
+ * @phase: hot-plug phase
+ * @func: Hot-plug function
+ * @order: Pre-defined order value
+ */
+int shp_register_handler(enum shp_phase phase, shp_func func, u32 order)
+{
+ struct list_head *head;
+ struct shp_handler *hdr, *cur;
+ u32 order_base;
+ int insert = 0;
+
+ if (!func || order > SHP_ORDER_MAX)
+ return -EINVAL;
+
+ if (shp_is_add_phase(phase))
+ head = &shp_add_list_head;
+ else
+ head = &shp_del_list_head;
+
+ order_base = shp_get_order_base(phase);
+
+ hdr = kzalloc(sizeof(*hdr), GFP_KERNEL);
+ if (!hdr)
+ return -ENOMEM;
+
+ hdr->shp_order = order + order_base;
+ hdr->shp_func = func;
+
+ /*
+ * Add this handler to the list in ascending order
+ */
+ mutex_lock(&shp_hdr_list_lock);
+ if (list_empty(head)) {
+ list_add(&hdr->shp_list, head);
+ } else {
+ list_for_each_entry(cur, head, shp_list)
+ if (cur->shp_order > hdr->shp_order) {
+ insert = 1;
+ break;
+ }
+
+ if (insert)
+ __list_add(&hdr->shp_list,
+ cur->shp_list.prev, &cur->shp_list);
+ else
+ list_add_tail(&hdr->shp_list, head);
+ }
+ mutex_unlock(&shp_hdr_list_lock);
+
+ return 0;
+}
+EXPORT_SYMBOL(shp_register_handler);
+
+/**
+ * shp_unregister_handler - unregister a hot-plug handler from the framework
+ * @phase: hot-plug phase
+ * @func: Hot-plug function
+ */
+int shp_unregister_handler(enum shp_phase phase, shp_func func)
+{
+ struct list_head *head;
+ struct shp_handler *cur;
+
+ if (!func)
+ return -EINVAL;
+
+ if (shp_is_add_phase(phase))
+ head = &shp_add_list_head;
+ else
+ head = &shp_del_list_head;
+
+ /*
+ * Delete this handler from the list
+ */
+ mutex_lock(&shp_hdr_list_lock);
+ list_for_each_entry(cur, head, shp_list)
+ if (cur->shp_func == func) {
+ list_del(&cur->shp_list);
+ kfree(cur);
+ break;
+ }
+ mutex_unlock(&shp_hdr_list_lock);
+
+ return 0;
+}
+EXPORT_SYMBOL(shp_unregister_handler);
+
+static void shp_start_req(struct work_struct *work)
+{
+ struct shp_work *shp_work = container_of(work, struct shp_work, work);
+ struct shp_request *req = shp_work->request;
+ struct shp_handler *hdr;
+ struct shp_device *shp_dev, *tmp;
+ struct list_head *head;
+ int rollback = 0;
+ int ret;
+
+ if (shp_is_add_op(req->operation))
+ head = &shp_add_list_head;
+ else
+ head = &shp_del_list_head;
+
+ if (shp_trace)
+ pr_info("Starting %s Operation\n",
+ shp_operation_string(req->operation));
+
+ /*
+ * Call hot-plug handlers in the list
+ */
+ mutex_lock(&shp_hdr_list_lock);
+ list_for_each_entry(hdr, head, shp_list) {
+ if (shp_trace)
+ pr_info("-> %s\n",
+ kallsyms_lookup((unsigned long)hdr->shp_func,
+ NULL, NULL, NULL, shp_ksym_buf));
+
+ ret = hdr->shp_func(req, 0);
+ if (ret) {
+ if (hdr->shp_order < SHP_COMMIT_ORDER_BASE) {
+ if (shp_trace)
+ pr_info("Initiating Rollback\n");
+ rollback = 1;
+ break;
+ } else {
+ pr_err("Commit handler failed: continuing\n");
+ continue;
+ }
+ }
+ }
+
+ /*
+ * If rollback is requested, call hot-plug handlers in the reversed
+ * order from the failed handler. The failed handler is not called
+ * again.
+ */
+ if (rollback) {
+ list_for_each_entry_continue_reverse(hdr, head, shp_list) {
+ if (shp_trace)
+ pr_info("RB-> %s\n",
+ kallsyms_lookup(
+ (unsigned long)hdr->shp_func,
+ NULL, NULL, NULL, shp_ksym_buf));
+
+ ret = hdr->shp_func(req, 1);
+ if (ret)
+ pr_err("Rollback handler failed: continuing\n");
+ }
+ }
+ mutex_unlock(&shp_hdr_list_lock);
+
+ /* free up the hot-plug request information */
+ list_for_each_entry_safe(shp_dev, tmp, &req->dev_list, list) {
+ list_del(&shp_dev->list);
+ kfree(shp_dev);
+ }
+ kfree(req);
+ kfree(shp_work);
+}
+
+/**
+ * shp_submit_req - submit a hot-plug request
+ * @req: Hot-plug request pointer
+ */
+int shp_submit_req(struct shp_request *req)
+{
+ struct shp_work *shp_work;
+
+ shp_work = kzalloc(sizeof(*shp_work), GFP_KERNEL);
+ if (!shp_work)
+ return -ENOMEM;
+
+ shp_work->request = req;
+ INIT_WORK(&shp_work->work, shp_start_req);
+
+ if (!queue_work(shp_workqueue, &shp_work->work)) {
+ kfree(shp_work);
+ return -EINVAL;
+ }
+
+ return 0;
+}
+EXPORT_SYMBOL(shp_submit_req);
+
+/**
+ * shp_alloc_request - allocate a hot-plug request
+ * @operation: Hot-plug operation
+ */
+struct shp_request *shp_alloc_request(enum shp_operation operation)
+{
+ struct shp_request *shp_req;
+
+ shp_req = kzalloc(sizeof(*shp_req), GFP_KERNEL);
+ if (!shp_req)
+ return NULL;
+
+ shp_req->operation = operation;
+ INIT_LIST_HEAD(&shp_req->dev_list);
+
+ return shp_req;
+}
+EXPORT_SYMBOL(shp_alloc_request);
+
+/**
+ * shp_add_dev_info - add shp_device to the hotplug request
+ * @shp_req: hot-plug request pointer
+ * @shp_dev: hot-plug device info pointer
+ */
+void shp_add_dev_info(struct shp_request *shp_req, struct shp_device *shp_dev)
+{
+ list_add_tail(&shp_dev->list, &shp_req->dev_list);
+}
+EXPORT_SYMBOL(shp_add_dev_info);
+
+static int __init shp_init(void)
+{
+ /*
+ * Allocate shp_workqueue with max_active set to 1. This serializes
+ * hot-plug and online/offline operations on the workqueue.
+ */
+ shp_workqueue = alloc_workqueue("hotplug", 0, 1);
+
+ return 0;
+}
+device_initcall(shp_init);
--
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