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Subject[RFC PATCH 02/11] drivers/base: Add hotplug framework code
Date
Added hotplug.c, which is the hotplug framework code.

hp_register_handler() allows modules to register their hotplug handlers
to the framework. hp_submit_req() provides the interface to submit
a hotplug or online/offline request. The request is then put into
hp_workqueue. hp_start_req() calls all registered handlers in ascending
order for each phase. If any handler failed in validate or execute phase,
hp_start_req() initiates the rollback procedure.

Signed-off-by: Toshi Kani <toshi.kani@hp.com>
---
drivers/base/Makefile | 1 +
drivers/base/hotplug.c | 283 +++++++++++++++++++++++++++++++++++++++++++++++++
2 files changed, 284 insertions(+)
create mode 100644 drivers/base/hotplug.c

diff --git a/drivers/base/Makefile b/drivers/base/Makefile
index 5aa2d70..af2e013 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-$(CONFIG_SOC_BUS) += soc.o
+obj-$(CONFIG_HOTPLUG) += hotplug.o

ccflags-$(CONFIG_DEBUG_DRIVER) := -DDEBUG

diff --git a/drivers/base/hotplug.c b/drivers/base/hotplug.c
new file mode 100644
index 0000000..9e85e25
--- /dev/null
+++ b/drivers/base/hotplug.c
@@ -0,0 +1,283 @@
+/*
+ * hotplug.c - Hot-plug framework for system devices
+ *
+ * Copyright (C) 2012 Hewlett-Packard Development Company, L.P.
+ * Toshi Kani <toshi.kani@hp.com>
+ *
+ * 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/hotplug.h>
+#include <linux/kallsyms.h>
+
+/*
+ * Hot-plug handler list
+ */
+struct hp_handler {
+ struct list_head hp_list;
+ int hp_order;
+ hp_func hp_func;
+};
+
+LIST_HEAD(hp_add_list_head);
+LIST_HEAD(hp_del_list_head);
+
+#define HP_VALIDATE_ORDER_BASE (HP_ORDER_MAX+1)
+#define HP_EXECUTE_ORDER_BASE ((HP_ORDER_MAX+1) << 1)
+#define HP_COMMIT_ORDER_BASE ((HP_ORDER_MAX+1) << 2)
+
+/*
+ * Hot-plug request work queue
+ */
+struct hp_work {
+ struct hp_request *request;
+ struct work_struct work;
+};
+
+static struct workqueue_struct *hp_workqueue;
+
+/* trace messages */
+static int hp_trace = 1;
+static char hp_ksym_buf[KSYM_NAME_LEN];
+
+static char *hp_operation_string(enum hp_operation operation)
+{
+ switch (operation) {
+ case HP_HOTPLUG_ADD:
+ return "Hot-Add";
+ case HP_HOTPLUG_DEL:
+ return "Hot-Delete";
+ case HP_ONLINE_ADD:
+ return "Online";
+ case HP_ONLINE_DEL:
+ return "Offline";
+ }
+
+ return "n/a";
+}
+
+static u32 hp_get_order_base(enum hp_phase phase)
+{
+ switch (phase) {
+ case HP_ADD_VALIDATE:
+ case HP_DEL_VALIDATE:
+ return HP_VALIDATE_ORDER_BASE;
+ case HP_ADD_EXECUTE:
+ case HP_DEL_EXECUTE:
+ return HP_EXECUTE_ORDER_BASE;
+ case HP_ADD_COMMIT:
+ case HP_DEL_COMMIT:
+ return HP_COMMIT_ORDER_BASE;
+ }
+
+ return 0;
+}
+
+/**
+ * hp_register_handler - register a hot-plug handler to the framework
+ * @phase: hot-plug phase
+ * @func: Hot-plug function
+ * @order: Pre-defined order value
+ */
+int hp_register_handler(enum hp_phase phase, hp_func func, u32 order)
+{
+ struct list_head *head;
+ struct hp_handler *hdr, *cur;
+ u32 order_base;
+ int insert = 0;
+
+ if (!func || order > HP_ORDER_MAX)
+ return -EINVAL;
+
+ if (hp_is_add_phase(phase))
+ head = &hp_add_list_head;
+ else
+ head = &hp_del_list_head;
+
+ order_base = hp_get_order_base(phase);
+
+ hdr = kzalloc(sizeof(*hdr), GFP_KERNEL);
+ if (!hdr)
+ return -ENOMEM;
+
+ hdr->hp_order = order + order_base;
+ hdr->hp_func = func;
+
+ /*
+ * Add this handler to the list in ascending order
+ */
+ if (list_empty(head)) {
+ list_add(&hdr->hp_list, head);
+ } else {
+ list_for_each_entry(cur, head, hp_list)
+ if (cur->hp_order > hdr->hp_order) {
+ insert = 1;
+ break;
+ }
+
+ if (insert)
+ __list_add(&hdr->hp_list,
+ cur->hp_list.prev, &cur->hp_list);
+ else
+ list_add_tail(&hdr->hp_list, head);
+ }
+
+ return 0;
+}
+EXPORT_SYMBOL(hp_register_handler);
+
+/**
+ * hp_unregister_handler - unregister a hot-plug handler from the framework
+ * @phase: hot-plug phase
+ * @func: Hot-plug function
+ */
+int hp_unregister_handler(enum hp_phase phase, hp_func func)
+{
+ /* REVISIT: implement later */
+ return 0;
+}
+EXPORT_SYMBOL(hp_unregister_handler);
+
+static void hp_start_req(struct work_struct *work)
+{
+ struct hp_work *hp_work = container_of(work, struct hp_work, work);
+ struct hp_request *req = hp_work->request;
+ struct hp_handler *hdr;
+ struct hp_device *hp_dev, *tmp;
+ struct list_head *head;
+ int rollback = 0;
+ int ret;
+
+ if (hp_is_add_op(req->operation))
+ head = &hp_add_list_head;
+ else
+ head = &hp_del_list_head;
+
+ if (hp_trace)
+ pr_info("Starting %s Operation\n",
+ hp_operation_string(req->operation));
+
+ /*
+ * Call hot-plug handlers in the list
+ */
+ list_for_each_entry(hdr, head, hp_list) {
+ if (hp_trace)
+ pr_info("-> %s\n",
+ kallsyms_lookup((unsigned long)hdr->hp_func,
+ NULL, NULL, NULL, hp_ksym_buf));
+
+ ret = hdr->hp_func(req, 0);
+ if (ret) {
+ if (hdr->hp_order < HP_COMMIT_ORDER_BASE) {
+ if (hp_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, hp_list) {
+ if (hp_trace)
+ pr_info("RB-> %s\n",
+ kallsyms_lookup(
+ (unsigned long)hdr->hp_func,
+ NULL, NULL, NULL, hp_ksym_buf));
+
+ ret = hdr->hp_func(req, 1);
+ if (ret)
+ pr_err("Rollback handler failed: continuing\n");
+ }
+ }
+
+ /* free up the hot-plug request information */
+ list_for_each_entry_safe(hp_dev, tmp, &req->dev_list, list) {
+ list_del(&hp_dev->list);
+ kfree(hp_dev);
+ }
+ kfree(req);
+ kfree(hp_work);
+}
+
+/**
+ * hp_submit_req - submit a hot-plug request
+ * @req: Hot-plug request pointer
+ */
+int hp_submit_req(struct hp_request *req)
+{
+ struct hp_work *hp_work;
+
+ hp_work = kzalloc(sizeof(*hp_work), GFP_KERNEL);
+ if (!hp_work)
+ return -ENOMEM;
+
+ hp_work->request = req;
+ INIT_WORK(&hp_work->work, hp_start_req);
+
+ if (!queue_work(hp_workqueue, &hp_work->work)) {
+ kfree(hp_work);
+ return -EINVAL;
+ }
+
+ return 0;
+}
+EXPORT_SYMBOL(hp_submit_req);
+
+/**
+ * hp_alloc_request - allocate a hot-plug request
+ * @operation: Hot-plug operation
+ */
+struct hp_request *hp_alloc_request(enum hp_operation operation)
+{
+ struct hp_request *hp_req;
+
+ hp_req = kzalloc(sizeof(*hp_req), GFP_KERNEL);
+ if (!hp_req)
+ return NULL;
+
+ hp_req->operation = operation;
+ INIT_LIST_HEAD(&hp_req->dev_list);
+
+ return hp_req;
+}
+EXPORT_SYMBOL(hp_alloc_request);
+
+/**
+ * hp_add_dev_info - add hp_device to the hotplug request
+ * @hp_req: hot-plug request pointer
+ * @hp_dev: hot-plug device info pointer
+ */
+void hp_add_dev_info(struct hp_request *hp_req, struct hp_device *hp_dev)
+{
+ list_add_tail(&hp_dev->list, &hp_req->dev_list);
+}
+EXPORT_SYMBOL(hp_add_dev_info);
+
+static int __init hp_init(void)
+{
+ /*
+ * Allocate hp_workqueue with max_active set to 1. This serializes
+ * hot-plug and online/offline operations on the workqueue.
+ */
+ hp_workqueue = alloc_workqueue("hotplug", 0, 1);
+
+ return 0;
+}
+device_initcall(hp_init);
--
1.7.11.7


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