Re: [RFC PATCH v2 10/16] ACPIHP: system device hotplug driver skeleton

From: Tang Chen <tangchen@cn.fujitsu.com>
To: Jiang Liu <jiang.liu@huawei.com>
Cc: Yinghai Lu <yinghai@kernel.org>,
	Yasuaki Ishimatsu <isimatu.yasuaki@jp.fujitsu.com>,
	Kenji Kaneshige <kaneshige.kenji@jp.fujitsu.com>,
	Wen Congyang <wency@cn.fujitsu.com>,
	Taku Izumi <izumi.taku@jp.fujitsu.com>,
	Tony Luck <tony.luck@intel.com>,
	Huang Ying <ying.huang@intel.com>,
	Bob Moore <robert.moore@intel.com>, Len Brown <lenb@kernel.org>,
	"Srivatsa S. Bhat" <srivatsa.bhat@linux.vnet.ibm.com>,
	Bjorn Helgaas <bhelgaas@google.com>,
	linux-kernel@vger.kernel.org, linux-acpi@vger.kernel.org,
	linux-pci@vger.kernel.org, Jiang Liu <liuj97@gmail.com>,
	Hanjun Guo <guohanjun@huawei.com>
Subject: Re: [RFC PATCH v2 10/16] ACPIHP: system device hotplug driver skeleton
Date: Thu, 09 Aug 2012 15:12:35 +0800	[thread overview]
Message-ID: <502362E3.8010901@cn.fujitsu.com> (raw)
In-Reply-To: <1344082443-4608-11-git-send-email-jiang.liu@huawei.com>

Hi Liu~

I compiled this driver as a module, acpihp_drv. And when I loaded this module, it
gave the following error message:

# modprobe acpihp_drv
(the command hangs up, no return after 10 min)

#dmesg
......
[  126.643350] BUG: unable to handle kernel NULL pointer dereference at 0000000000000078
[  126.644007] IP: [<ffffffff814c0cd3>] mutex_lock+0x19/0x37
[  126.644007] PGD 105277a067 PUD 104f823067 PMD 0 
[  126.644007] Oops: 0002 [#1] SMP 
[  126.644007] Modules linked in: acpihp_drv(+) ebtable_nat ebtables ipt_MASQUERADE iptable_nat nf_nat iptable_mangle bridge stp llc sunrpc cpufreq_ondemand acpi_cpufreq freq_table mperf ip6t_REJECT nf_conntrack_ipv6 nf_defrag_ipv6 ip6table_filter ip6_tables ipv6 vhost_net macvtap macvlan tun uinput iTCO_wdt iTCO_vendor_support coretemp kvm_intel kvm crc32c_intel microcode lpc_ich mfd_core pcspkr i2c_i801 i2c_core ioatdma e1000e acpi_memhotplug i7core_edac edac_core igb dca mptsas mptscsih mptbase scsi_transport_sas
[  126.644007] CPU 10 
[  126.644007] Pid: 2821, comm: modprobe Tainted: G       A     3.6.0-rc1+ #6 FUJITSU-SV PRIMEQUEST 1800E/SB
[  126.644007] RIP: 0010:[<ffffffff814c0cd3>]  [<ffffffff814c0cd3>] mutex_lock+0x19/0x37
[  126.644007] RSP: 0018:ffff8810589a9de8  EFLAGS: 00010246
[  126.644007] RAX: 0000000000000000 RBX: 0000000000000078 RCX: 0000000000000000
[  126.644007] RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000000000078
[  126.644007] RBP: ffff8810589a9e08 R08: 0000000000000000 R09: ffff8810589a9d88
[  126.644007] R10: 00000000000013e5 R11: 00000000000013e5 R12: ffffffffa01460d0
[  126.644007] R13: 0000000000000000 R14: ffffffffa014732b R15: 00000000000000bf
[  126.644007] FS:  00007fecb1802700(0000) GS:ffff88105e640000(0000) knlGS:0000000000000000
[  126.644007] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[  126.644007] CR2: 0000000000000078 CR3: 0000001052772000 CR4: 00000000000007e0
[  126.644007] DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
[  126.644007] DR3: 0000000000000000 DR6: 00000000ffff0ff0 DR7: 0000000000000400
[  126.644007] Process modprobe (pid: 2821, threadinfo ffff8810589a8000, task ffff8810592f8000)
[  126.644007] Stack:
[  126.644007]  ffff8810589a9e08 ffffffff810be37f ffffffffa0146220 ffffffff81a7b390
[  126.644007]  ffff8810589a9e58 ffffffff81317eb3 ffff8810589a9e48 0000000000000000
[  126.644007]  ffffffff81a342c0 ffffffff81a342e0 0000000000000000 ffffffffa0146220
[  126.644007] Call Trace:
[  126.644007]  [<ffffffff810be37f>] ? tracepoint_module_notify+0xd9/0x14a
[  126.644007]  [<ffffffff81317eb3>] class_interface_register+0x4a/0xbc
[  126.644007]  [<ffffffffa00b8000>] ? 0xffffffffa00b7fff
[  126.644007]  [<ffffffffa00b8010>] acpihp_drv_init+0x10/0x12 [acpihp_drv]
[  126.644007]  [<ffffffff8100207f>] do_one_initcall+0x7f/0x139
[  126.644007]  [<ffffffff81093414>] sys_init_module+0x12d3/0x14e3
[  126.644007]  [<ffffffff81264b0d>] ? ddebug_dyndbg_boot_param_cb+0x45/0x45
[  126.644007]  [<ffffffff814c9469>] system_call_fastpath+0x16/0x1b
[  126.644007] Code: 48 8b 04 25 80 c6 00 00 48 89 43 18 31 c0 5b 5b c9 c3 55 48 89 e5 53 48 83 ec 18 66 66 66 66 90 48 89 fb e8 5a 0c 00 00 48 89 df <f0> ff 0f 79 05 e8 06 ff ff ff 65 48 8b 04 25 80 c6 00 00 48 89 
[  126.644007] RIP  [<ffffffff814c0cd3>] mutex_lock+0x19/0x37
[  126.644007]  RSP <ffff8810589a9de8>
[  126.644007] CR2: 0000000000000078
[  129.981335] ---[ end trace da17e9c9de8dd560 ]---
[  139.085895] nr_pdflush_threads exported in /proc is scheduled for removal
[  139.167394] sysctl: The scan_unevictable_pages sysctl/node-interface has been disabled for lack of a legitimate use case.  If you have one, please send an email to linux-mm@kvack.org.

Looks like it dereferenced a NULL pointer here.
May be it was my mistake that I didn't configure the environment correctly.
Would you please give me some advice ?

Thanks. :)

On 08/04/2012 08:13 PM, Jiang Liu wrote:
> From: Jiang Liu <jiang.liu@huawei.com>
> 
> This patch implements a skeleton for ACPI based system device hotplug driver.
> This device class driver will be bound to and manage ACPI hotplug slots.
> 
> This is the default hotplug driver for ACPI based system device hotplug.
> 
> Signed-off-by: Jiang Liu <liuj97@gmail.com>
> Signed-off-by: Hanjun Guo <guohanjun@huawei.com>
> ---
>  drivers/acpi/Kconfig              |   12 ++
>  drivers/acpi/hotplug/Makefile     |    3 +
>  drivers/acpi/hotplug/acpihp_drv.h |   62 +++++++
>  drivers/acpi/hotplug/drv_main.c   |  331 +++++++++++++++++++++++++++++++++++++
>  4 files changed, 408 insertions(+)
>  create mode 100644 drivers/acpi/hotplug/acpihp_drv.h
>  create mode 100644 drivers/acpi/hotplug/drv_main.c
> 
> diff --git a/drivers/acpi/Kconfig b/drivers/acpi/Kconfig
> index c9f7918..89047a3 100644
> --- a/drivers/acpi/Kconfig
> +++ b/drivers/acpi/Kconfig
> @@ -354,6 +354,18 @@ config ACPI_HOTPLUG_ENUM_EJ0
>  
>  	  It's the default method to detect ACPI hotplug slots.
>  
> +config ACPI_HOTPLUG_DRIVER
> +	tristate "ACPI Based System Device Hotplug Driver"
> +	depends on ACPI_HOTPLUG
> +	default y
> +	help
> +	  This driver enables ACPI based system device hotplug, including
> +	  physical processor, memory device, IO host bridge and computer
> +	  node etc.
> +
> +	  To compile this driver as a module, choose M here:
> +	  the module will be called acpihp_drv.
> +
>  config ACPI_CONTAINER
>  	tristate "Container and Module Devices (EXPERIMENTAL)"
>  	depends on EXPERIMENTAL
> diff --git a/drivers/acpi/hotplug/Makefile b/drivers/acpi/hotplug/Makefile
> index 25fac24..d69832f 100644
> --- a/drivers/acpi/hotplug/Makefile
> +++ b/drivers/acpi/hotplug/Makefile
> @@ -8,3 +8,6 @@ acpihp-y					= core.o device.o
>  obj-$(CONFIG_ACPI_HOTPLUG_ENUM)			+= acpihp_enum.o
>  acpihp_enum-y					= slot_enum.o
>  acpihp_enum-y					+= slot_enum_ej0.o
> +
> +obj-$(CONFIG_ACPI_HOTPLUG_DRIVER)		+= acpihp_drv.o
> +acpihp_drv-y					= drv_main.o
> diff --git a/drivers/acpi/hotplug/acpihp_drv.h b/drivers/acpi/hotplug/acpihp_drv.h
> new file mode 100644
> index 0000000..18330f7
> --- /dev/null
> +++ b/drivers/acpi/hotplug/acpihp_drv.h
> @@ -0,0 +1,62 @@
> +/*
> + * Copyright (C) 2011 Huawei Tech. Co., Ltd.
> + * Copyright (C) 2011 Jiang Liu <jiang.liu@huawei.com>
> + * Copyright (C) 2011 Hanjun Guo <guohanjun@huawei.com>
> + *
> + * ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> + *
> + * 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
> + *
> + * ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> + */
> +
> +#ifndef	__ACPIHP_DRV_H__
> +#define	__ACPIHP_DRV_H__
> +
> +/* Commands to change state of a hotplug slot */
> +enum acpihp_drv_cmd {
> +	ACPIHP_DRV_CMD_NOOP = 0,
> +	ACPIHP_DRV_CMD_POWERON = 0x1,
> +	ACPIHP_DRV_CMD_CONNECT = 0x2,
> +	ACPIHP_DRV_CMD_CONFIGURE = 0x4,
> +	ACPIHP_DRV_CMD_UNCONFIGURE = 0x8,
> +	ACPIHP_DRV_CMD_DISCONNECT = 0x10,
> +	ACPIHP_DRV_CMD_POWEROFF = 0x20,
> +	ACPIHP_DRV_CMD_CANCEL = 0x40,
> +	ACPIHP_DRV_CMD_MAX
> +};
> +
> +/* Hotplug operations may be triggered by firmware or OS */
> +enum acpihp_dev_event {
> +	ACPIHP_DRV_EVENT_FROM_FW,
> +	ACPIHP_DRV_EVENT_FROM_OS
> +};
> +
> +struct acpihp_slot_drv {
> +	enum acpihp_dev_event	event_flag;
> +	struct mutex		op_mutex; /* Prevent concurrent hotplugs. */
> +	struct list_head	depend_list; /* Dependency relationship */
> +	atomic_t		cancel_status;
> +	atomic_t		cancel_flag;
> +	struct acpihp_cancel_context	cancel_ctx;
> +};
> +
> +void acpihp_drv_get_data(struct acpihp_slot *slot,
> +			 struct acpihp_slot_drv **data);
> +int acpihp_drv_enumerate_devices(struct acpihp_slot *slot);
> +void acpihp_drv_update_slot_state(struct acpihp_slot *slot);
> +int acpihp_drv_update_slot_status(struct acpihp_slot *slot);
> +
> +#endif	/* __ACPIHP_DRV_H__ */
> diff --git a/drivers/acpi/hotplug/drv_main.c b/drivers/acpi/hotplug/drv_main.c
> new file mode 100644
> index 0000000..538772d
> --- /dev/null
> +++ b/drivers/acpi/hotplug/drv_main.c
> @@ -0,0 +1,331 @@
> +/*
> + * Copyright (C) 2011 Huawei Tech. Co., Ltd.
> + * Copyright (C) 2011 Jiang Liu <jiang.liu@huawei.com>
> + * Copyright (C) 2011 Hanjun Guo <guohanjun@huawei.com>
> + *
> + * ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> + *
> + * 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
> + *
> + * ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> + */
> +
> +#include <linux/kernel.h>
> +#include <linux/errno.h>
> +#include <linux/types.h>
> +#include <linux/list.h>
> +#include <linux/mutex.h>
> +#include <linux/kthread.h>
> +#include <linux/delay.h>
> +#include <linux/acpi.h>
> +#include <acpi/acpi_hotplug.h>
> +#include "acpihp_drv.h"
> +
> +static struct class_interface acpihp_drv_interface;
> +
> +void acpihp_drv_get_data(struct acpihp_slot *slot,
> +			 struct acpihp_slot_drv **data)
> +{
> +	*data = NULL;
> +	acpihp_slot_get_drv_data(slot, &acpihp_drv_interface, (void **)data);
> +}
> +
> +/* Update slot state according to state of devices connecting to it. */
> +void acpihp_drv_update_slot_state(struct acpihp_slot *slot)
> +{
> +	enum acpihp_dev_type type;
> +	enum acpihp_slot_state state;
> +	struct klist_iter iter;
> +	struct klist_node *ip;
> +	struct acpihp_dev_node *dp;
> +	bool connected = false;
> +	bool configured = false;
> +
> +	if (!acpihp_slot_present(slot)) {
> +		state = ACPIHP_SLOT_STATE_ABSENT;
> +		goto out;
> +	} else if (!acpihp_slot_powered(slot)) {
> +		state = ACPIHP_SLOT_STATE_PRESENT;
> +		goto out;
> +	}
> +
> +	for (type = ACPIHP_DEV_TYPE_UNKNOWN;
> +	     type < ACPIHP_DEV_TYPE_MAX && !configured;
> +	     type++) {
> +		klist_iter_init(&slot->dev_lists[type], &iter);
> +		while ((ip = klist_next(&iter)) != NULL) {
> +			connected = true;
> +			dp = container_of(ip, struct acpihp_dev_node, node);
> +			if (dp->state == DEVICE_STATE_CONFIGURED) {
> +				configured = true;
> +				break;
> +			}
> +		}
> +		klist_iter_exit(&iter);
> +	}
> +
> +	if (configured)
> +		state = ACPIHP_SLOT_STATE_CONFIGURED;
> +	else if (connected)
> +		state = ACPIHP_SLOT_STATE_CONNECTED;
> +	else
> +		state = ACPIHP_SLOT_STATE_POWERED;
> +
> +out:
> +	acpihp_slot_change_state(slot, state);
> +}
> +
> +/* Update slot state according to status of devices connecting to it. */
> +int acpihp_drv_update_slot_status(struct acpihp_slot *slot)
> +{
> +	int ret = 0;
> +	enum acpihp_dev_type type;
> +	struct klist_iter iter;
> +	struct klist_node *ip;
> +	struct acpihp_dev_node *np;
> +	struct acpi_device *dev;
> +	struct acpihp_dev_info *info;
> +
> +	if (!slot)
> +		return -EINVAL;
> +
> +	info = kzalloc(sizeof(*info), GFP_KERNEL);
> +	if (!info)
> +		return -ENOMEM;
> +
> +	for (type = ACPIHP_DEV_TYPE_MEM; type <= ACPIHP_DEV_TYPE_HOST_BRIDGE;
> +	     type++) {
> +		klist_iter_init(&slot->dev_lists[type], &iter);
> +		while ((ip = klist_next(&iter)) != NULL) {
> +			np = container_of(ip, struct acpihp_dev_node, node);
> +			dev = container_of(np->dev, struct acpi_device, dev);
> +			ret = acpihp_dev_get_info(dev, info);
> +			if (ret) {
> +				ACPIHP_DEBUG("fails to get info about %s.\n",
> +					     dev_name(&dev->dev));
> +				goto out;
> +			}
> +
> +			if (info->status & ACPIHP_DEV_STATUS_FAULT)
> +				acpihp_slot_set_flag(slot,
> +						ACPIHP_SLOT_FLAG_FAULT);
> +			if (info->status & ACPIHP_DEV_STATUS_IRREMOVABLE)
> +				acpihp_slot_set_flag(slot,
> +						ACPIHP_SLOT_FLAG_IRREMOVABLE);
> +		}
> +	}
> +
> +out:
> +	kfree(info);
> +
> +	return ret;
> +}
> +EXPORT_SYMBOL(acpihp_drv_update_slot_status);
> +
> +/* Add ACPI device to hotplug slot's device list */
> +static acpi_status acpihp_drv_enum_device(struct acpi_device *dev, void *argp)
> +{
> +	int ret = -ENOMEM;
> +	acpi_status rv = AE_OK;
> +	enum acpihp_dev_type type;
> +	enum acpihp_dev_state state;
> +	struct acpihp_dev_info *info;
> +	struct acpihp_slot *slot = (struct acpihp_slot *)argp;
> +
> +	if (acpihp_dev_get_type(dev->handle, &type)) {
> +		ACPIHP_DEBUG("fails to get device type of %s.\n",
> +			     dev_name(&dev->dev));
> +		return AE_ERROR;
> +	} else if (type == ACPIHP_DEV_TYPE_MAX) {
> +		/*
> +		 * Some ACPI objects for IO devices, such as PCI/IDE etc, only
> +		 * implement _ADR instead of _HID/_CID, skip them.
> +		 */
> +		return AE_CTRL_DEPTH;
> +	}
> +
> +	info = kzalloc(sizeof(*info), GFP_KERNEL);
> +	if (info)
> +		ret = acpihp_dev_get_info(dev, info);
> +
> +	if (!ret) {
> +		if (info->status & ACPIHP_DEV_STATUS_STARTED)
> +			state = DEVICE_STATE_CONFIGURED;
> +		else
> +			state = DEVICE_STATE_CONNECTED;
> +
> +		if (info->status & ACPIHP_DEV_STATUS_IRREMOVABLE)
> +			acpihp_slot_set_flag(slot,
> +					     ACPIHP_SLOT_FLAG_IRREMOVABLE);
> +		if (info->status & ACPIHP_DEV_STATUS_FAULT)
> +			acpihp_slot_set_flag(slot, ACPIHP_SLOT_FLAG_FAULT);
> +
> +		if (acpihp_slot_add_device(slot, type, state, &dev->dev)) {
> +			ACPIHP_DEBUG("fails to add %s to slot %s.\n",
> +				     dev_name(&dev->dev), slot->name);
> +			rv = AE_ERROR;
> +		}
> +	} else {
> +		ACPIHP_DEBUG("fails to query device info of %s.\n",
> +			     dev_name(&dev->dev));
> +	}
> +
> +	kfree(info);
> +
> +	return rv;
> +}
> +
> +/*
> + * Enumerator all devices connecting to a slot and add them onto slot's
> + * device lists.
> + */
> +int acpihp_drv_enumerate_devices(struct acpihp_slot *slot)
> +{
> +	return acpihp_walk_devices(slot->handle, acpihp_drv_enum_device, slot);
> +}
> +
> +static void acpihp_drv_remove_devices(struct acpihp_slot *slot)
> +{
> +	enum acpihp_dev_type type;
> +
> +	for (type = ACPIHP_DEV_TYPE_UNKNOWN; type < ACPIHP_DEV_TYPE_MAX; type++)
> +		acpihp_remove_device_list(&slot->dev_lists[type]);
> +}
> +
> +/* Callback function for ACPI system event notification. */
> +static void acpihp_drv_event_handler(acpi_handle handle, u32 event,
> +				     void *context)
> +{
> +	/* TODO: handle ACPI hotplug events */
> +}
> +
> +static acpi_status acpihp_drv_install_handler(struct acpihp_slot *slot)
> +{
> +	acpi_status status;
> +
> +	status = acpi_install_notify_handler(slot->handle, ACPI_SYSTEM_NOTIFY,
> +					     acpihp_drv_event_handler, slot);
> +	ACPIHP_DEBUG("%s to install event handler for %s.\n",
> +		     ACPI_SUCCESS(status) ? "succeeds" : "fails", slot->name);
> +
> +	return status;
> +}
> +
> +static void acpihp_drv_uninstall_handler(struct acpihp_slot *slot)
> +{
> +	acpi_status status;
> +
> +	status = acpi_remove_notify_handler(slot->handle, ACPI_SYSTEM_NOTIFY,
> +					    acpihp_drv_event_handler);
> +	ACPIHP_DEBUG("%s to uninstall event handler for %s.\n",
> +		ACPI_SUCCESS(status) ? "succeeds" : "fails", slot->name);
> +}
> +
> +static int acpihp_drv_slot_add(struct device *dev, struct class_interface *intf)
> +{
> +	struct acpihp_slot_drv *drv_data;
> +	struct acpihp_slot *slot = container_of(dev, struct acpihp_slot, dev);
> +
> +	/*
> +	 * Try to hold a reference to the slot_ops structure to prevent
> +	 * the platform specific enumerator driver from unloading.
> +	 */
> +	if (!slot->slot_ops || !try_module_get(slot->slot_ops->owner)) {
> +		ACPIHP_DEBUG("fails to get reference to slot_ops for %s.\n",
> +			     slot->name);
> +		return -EINVAL;
> +	}
> +
> +	/* install ACPI event notification handler for slot */
> +	if (ACPI_FAILURE(acpihp_drv_install_handler(slot))) {
> +		ACPIHP_DEBUG("fails to install event handler for %s.\n",
> +			     slot->name);
> +		module_put(slot->slot_ops->owner);
> +		return -EBUSY;
> +	}
> +
> +	/* Enumerate all devices if slot is already powered. */
> +	if (!acpihp_slot_powered(slot))
> +		ACPIHP_DEBUG("slot %s is powered off.\n", slot->name);
> +	else if (acpihp_drv_enumerate_devices(slot))
> +		acpihp_slot_set_flag(slot, ACPIHP_SLOT_FLAG_IRREMOVABLE);
> +
> +	acpihp_drv_update_slot_state(slot);
> +
> +	drv_data = kzalloc(sizeof(*drv_data), GFP_KERNEL);
> +	if (drv_data) {
> +		drv_data->event_flag = ACPIHP_DRV_EVENT_FROM_FW;
> +		mutex_init(&drv_data->op_mutex);
> +		INIT_LIST_HEAD(&drv_data->depend_list);
> +	}
> +	if (drv_data == NULL ||
> +	    acpihp_slot_attach_drv_data(slot, intf, (void *)drv_data)) {
> +		ACPIHP_DEBUG("fails to attach driver data for %s.\n",
> +			     slot->name);
> +		acpihp_drv_remove_devices(slot);
> +		module_put(slot->slot_ops->owner);
> +		kfree(drv_data);
> +		return -ENOMEM;
> +	}
> +
> +	ACPIHP_INFO("found hotplug slot %s.\n", slot->full_path);
> +
> +	return 0;
> +}
> +
> +static void acpihp_drv_intf_remove(struct device *dev,
> +				  struct class_interface *intf)
> +{
> +	struct acpihp_slot_drv *drv_data = NULL;
> +	struct acpihp_slot *slot =
> +			container_of(dev, struct acpihp_slot, dev);
> +
> +	ACPIHP_INFO("remove hotplug slot %s.\n", slot->full_path);
> +
> +	acpihp_drv_uninstall_handler(slot);
> +	acpihp_drv_remove_devices(slot);
> +	acpihp_slot_detach_drv_data(slot, intf, (void **)&drv_data);
> +	if (drv_data != NULL)
> +		kfree(drv_data);
> +
> +	module_put(slot->slot_ops->owner);
> +}
> +
> +/*
> + * register a class driver onto the acpihp_slot_class to manage all system
> + * device hotplug slots.
> + */
> +static struct class_interface acpihp_drv_interface = {
> +	.class		= &acpihp_slot_class,
> +	.add_dev	= acpihp_drv_slot_add,
> +	.remove_dev	= acpihp_drv_intf_remove,
> +};
> +
> +static int __init acpihp_drv_init(void)
> +{
> +	return class_interface_register(&acpihp_drv_interface);
> +}
> +
> +static void __exit acpihp_drv_exit(void)
> +{
> +	class_interface_unregister(&acpihp_drv_interface);
> +}
> +
> +module_init(acpihp_drv_init);
> +module_exit(acpihp_drv_exit);
> +
> +MODULE_LICENSE("GPL v2");
> +MODULE_AUTHOR("Jiang Liu <jiang.liu@huawei.com>");
> +MODULE_AUTHOR("Hanjun Guo <guohanjun@huawei.com>");

-- 
Best Regards,
Tang chen