转自：https://blog.csdn.net/u010961173/article/details/96422441
1 概述
（1）mailbox是一种框架，通过消息队列和中断驱动信号处理多处理器间的通讯；
（2）mailbox的实现分为contoller和client。简单的说就是client 可以通过controller提供的channel发送信息给controller；
（3）在drivers/mailbox下实现的都是controller的源码；
具体到某个厂商的硬件，则描述如下：
Kconfig文件：内核开关，用于配置mbox模块是否编译到内核；
config ARM_MHU
tristate "ARM MHU Mailbox"
depends on ARM_AMBA help
Say Y here if you want to build the ARM MHU controller driver. The controller has 3 mailbox channels, the last of which can be used in Secure mode only.
Makefile文件：根据Kconfig编译相应的模块；
我们知道要实现mailbox的源文件其实只有两个
obj-$(CONFIG_MAILBOX) += mailbox.o
obj-$(CONFIG_ARM_MHU) += arm_mhu.o
其中，mailbox.c 是kernel提供的framework，arm_mhu.c 则是具体厂商的实现
（4）client 通过mbox_send_message给controller发送数据的时候必须指定channel；
int mbox_send_message(struct mbox_chan *chan, void *mssg)
（5）client 在通过mbox_send_message给controller发送数据的时候必须指定channel,channel可以通过以下方式获得。
目前kernel提供了两种方法得到mailbox的channel
struct mbox_chan *mbox_request_channel_byname(struct mbox_client *cl,const char *name);
struct mbox_chan *mbox_request_channel(struct mbox_client *cl, int index);
使用完成后调用mbox_free_channel 释放channel，这样别人就可以继续使用这个channel；
void mbox_free_channel(struct mbox_chan *chan); /* may sleep */
其中，mbox_request_channel_byname是mbox_request_channel的一个封装。
2 基本框架
目录：
drivers/mailbox
mailbox.c/mailbox.h/mailbox-test.c/<vendor>-mailbox.c
3 关键数据结构
struct mbox_controller {
struct device *dev; // 特定mailbox驱动probe时赋值 dev = &pdev->dev
const struct mbox_chan_ops *ops; // mailbox channel需要实现的功能函数
struct mbox_chan *chans; // mailbox channel指针数组
int num_chans; // mailbox channel个数
bool txdone_irq; // 通过中断来判断上次传输是否完成
bool txdone_poll; // 通过poll机制来判断上次传输是否完成
unsigned txpoll_period; // POLL 周期, 以ms计
struct mbox_chan *(*of_xlate)(struct mbox_controller *mbox,
const struct of_phandle_args *sp); // 获取特定channel的回调函数
/* Internal to API */
struct hrtimer poll_hrt;
struct list_head node;
};
struct mbox_chan {
struct mbox_controller *mbox; // contronller指针
unsigned txdone_method;
struct mbox_client *cl; // client指针
struct completion tx_complete; //
void *active_req;
unsigned msg_count, msg_free;
void *msg_data[MBOX_TX_QUEUE_LEN];
spinlock_t lock; /* Serialise access to the channel */
void *con_priv;
};
struct mbox_chan_ops {
int (*send_data)(struct mbox_chan *chan, void *data); // 发送数据（需要last data sent）
int (*startup)(struct mbox_chan *chan); // 特定mailbox 启动
void (*shutdown)(struct mbox_chan *chan); // 特定mailbox 关闭
bool (*last_tx_done)(struct mbox_chan *chan); // 如果TXDONE_BY_POLL 该回调会被使用
bool (*peek_data)(struct mbox_chan *chan); // 检测是否有数据
};
struct mbox_client {
struct device *dev; // client 设备
bool tx_block; // block until last data is all transmitted
unsigned long tx_tout; // max block period for timeout
bool knows_txdone; // txdone 回调，如果controller已经有txdone，则该配置无效
void (*rx_callback)(struct mbox_client *cl, void *mssg); // 收到数据
void (*tx_prepare)(struct mbox_client *cl, void *mssg); // 准备数据
void (*tx_done)(struct mbox_client *cl, void *mssg, int r); // 检测txdone
};
4 函数接口
4.1 mailbox controller api
文件：kernel/include/linux/mailbox_controller.h
（1）注册、注销控制器
int mbox_controller_register(struct mbox_controller *mbox); /* can sleep */--------probe中调用
void mbox_controller_unregister(struct mbox_controller *mbox); /* can sleep */-------probe中调用
（2）（对外接口）将底层收到的数据回调给上层应用
void mbox_chan_received_data(struct mbox_chan *chan, void *data); /* atomic */
（3）通知上层当前数据已经发送完成
void mbox_chan_txdone(struct mbox_chan *chan, int r); /* atomic */
4.2 mailbox client api
文件：kernel/include/linux/mailbox_client.h
（1）发送数据前，申请通道
struct mbox_chan *mbox_request_channel_byname(struct mbox_client *cl,
const char *name);
struct mbox_chan *mbox_request_channel(struct mbox_client *cl, int index);
（2）数据发送
int mbox_send_message(struct mbox_chan *chan, void *mssg);
void mbox_client_txdone(struct mbox_chan *chan, int r); /* atomic */
（3）数据记录
bool mbox_client_peek_data(struct mbox_chan *chan); /* atomic */
（4）释放通道
void mbox_free_channel(struct mbox_chan *chan); /* may sleep */
5 Device Tree中的写法
kernel4.14/Documentation/devicetree/bindings/mailbox/hisilicon,hi6220-mailbox.txt
Hisilicon Hi6220 Mailbox Driver
===============================
Hisilicon Hi6220 mailbox supports up to 32 channels. Each channel
is unidirectional with a maximum message size of 8 words. I/O is
performed using register access (there is no DMA) and the cell
raises an interrupt when messages are received.
Mailbox Device Node（Controller）:（设备节点相关的设备树）
====================
Required properties:
--------------------
- compatible: Shall be "hisilicon,hi6220-mbox"
- reg: Contains the mailbox register address range (base
address and length); the first item is for IPC
registers, the second item is shared buffer for
slots.
- #mbox-cells: Common mailbox binding property to identify the number
of cells required for the mailbox specifier. Must be 3.
<&phandle slot_id dst_irq ack_irq>
phandle: Label name of mailbox controller
slot_id: Slot id used either for TX or RX
dst_irq: IRQ identifier index number which used by MCU
ack_irq: IRQ identifier index number with generating a
TX/RX interrupt to application processor,
mailbox driver uses it to acknowledge interrupt
- interrupts: Contains the interrupt information for the mailbox
device. The format is dependent on which interrupt
controller the SoCs use.
Optional Properties:
--------------------
- hi6220,mbox-tx-noirq: Property of MCU firmware's feature, so mailbox driver
use this flag to ask MCU to enable "automatic idle
flag" mode or IRQ generated mode to acknowledge a TX
completion.
Example:
--------
mailbox: mailbox@f7510000 {
compatible = "hisilicon,hi6220-mbox";
reg = <0x0 0xf7510000 0x0 0x1000>, /* IPC_S */
<0x0 0x06dff800 0x0 0x0800>; /* Mailbox */
interrupt-parent = <&gic>;
interrupts = <GIC_SPI 94 IRQ_TYPE_LEVEL_HIGH>;
#mbox-cells = <3>;
};
Mailbox client（client相关的设备树）
===============
Required properties:
--------------------
- compatible: Many (See the client docs).
- mboxes: Standard property to specify a Mailbox (See ./mailbox.txt)
Cells must match 'mbox-cells' (See Mailbox Device Node above).
Optional Properties:
--------------------
- mbox-names: Name given to channels seen in the 'mboxes' property.
Example:
--------
stub_clock: stub_clock {
compatible = "hisilicon,hi6220-stub-clk";
hisilicon,hi6220-clk-sram = <&sram>;
#clock-cells = <1>;
mbox-names = "mbox-tx", "mbox-rx";
mboxes = <&mailbox 1 0 11>, <&mailbox 0 1 10>;
};
Example：
kernel4.14/arch/arm64/boot/dts/hisilicon/hi6220.dtsi
mailbox: mailbox@f7510000 {
compatible = "hisilicon,hi6220-mbox";
reg = <0x0 0xf7510000 0x0 0x1000>, /* IPC_S */
<0x0 0x06dff800 0x0 0x0800>; /* Mailbox */
interrupt-parent = <&gic>;
interrupts = <GIC_SPI 94 IRQ_TYPE_LEVEL_HIGH>;
#mbox-cells = <3>;
};
Example:
--------
stub_clock: stub_clock {
compatible = "hisilicon,hi6220-stub-clk";
hisilicon,hi6220-clk-sram = <&sram>;
#clock-cells = <1>;
mbox-names = "mbox-tx", "mbox-rx";
mboxes = <&mailbox 1 0 11>, <&mailbox 0 1 10>; <phandle channel_index dst_irq ack_irq>
};
6 原理详解
6.1 原理概述
（1）driver 通过mbox_controller_register 注册controller；
（2）client 通过mbox_request_channel调用driver->startup；
（3）client 通过mbox_send_message调用driver->send_data，并等待txdone；
（4）driver 收到remote的中断读取数据调用mbox_chan_received_data将数据放到 client->rx_buffer中；
6.1.1 mailbox driver流程
（1）配置controller属性:
（2）申请chan，配置chan个数
（3）配置of_xlate回调，获取chan
（4）配置chan_ops
（5）配置txdone判断方式
（6）通过mailbox_controller_register 注册controller；
6.1.2 mailbox client 流程
（1）通过mbox_request_channel_byname 根据"mbox-names"申请channel；
（2）创建mbox设备；
（3）通过mbox设备的write/read 函数访问controller；
其中，
write 通过调用mbox_send_message，add_to_rbuf拷贝msg到chan->msg_data[MAX = 20]，msg_submit读取msg_data[idx]，放到tx_prepare中，调用具体驱动的send message写寄存器；
read 通过irq驱动，irq读取寄存器得到消息，调用mailbox.c中的mbox_chan_received_data，再调用client的rx_callback将得到的数据放到client->rx_buffer中；
6.2 Mailbox Controller驱动
6.2.1 Mailbox Controller驱动初始化
6.2.1.1 mbox controller初始化函数
core_initcall(hi6220_mbox_init)
>>>platform_driver_register(&hi6220_mbox_driver);
module_exit(hi6220_mbox_exit);
>>>platform_driver_unregister(&hi6220_mbox_driver);
static struct platform_driver hi6220_mbox_driver = {
.driver = {
.name = "hi6220-mbox",
.owner = THIS_MODULE,
.of_match_table = hi6220_mbox_of_match,
},
.probe = hi6220_mbox_probe,//mbox controller drivers 初始化函数
.remove = hi6220_mbox_remove, //mbox controller drivers 逆初始化函数
};
static const struct of_device_id hi6220_mbox_of_match[] = {
{ .compatible = "hisilicon,hi6220-mbox", },
{},
};
6.2.1.2 调用probe/remove 函数
probe()函数主要用于初始化mbox controller.
hi6220_mbox_probe(struct platform_device *pdev)
>>>mbox = devm_kzalloc(dev, sizeof(*mbox), GFP_KERNEL);//分配vendor设备结构体struct hi6220_mbox *mbox
>>>初始化struct hi6220_mbox *mbox中的相关成员变量
>>>mbox->mchan = devm_kzalloc(dev,mbox->chan_num * sizeof(*mbox->mchan), GFP_KERNEL);//为chan_num个struct hi6220_mbox_chan申请内存
>>>mbox->chan = devm_kzalloc(dev,mbox->chan_num * sizeof(*mbox->chan), GFP_KERNEL);//为chan_num个struct mbox_chan申请内存
>>>mbox->irq = platform_get_irq(pdev, 0);
>>>res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
mbox->ipc = devm_ioremap_resource(dev, res);
>>> res = platform_get_resource(pdev, IORESOURCE_MEM, 1);
mbox->base = devm_ioremap_resource(dev, res);
>>>申请中断
err = devm_request_irq(dev, mbox->irq, hi6220_mbox_interrupt, 0, dev_name(dev), mbox);//其中，hi6220_mbox_interrupt为中断mbox->irq对应的服务函数
>>>初始化controller
mbox->controller.dev = dev;
mbox->controller.chans = &mbox->chan[0];
mbox->controller.num_chans = mbox->chan_num;
mbox->controller.ops = &hi6220_mbox_ops;
mbox->controller.of_xlate = hi6220_mbox_xlate;
for (i = 0; i < mbox->chan_num; i++) {
mbox->chan[i].con_priv = &mbox->mchan[i];
mbox->irq_map_chan[i] = NULL;
mbox->mchan[i].parent = mbox;
mbox->mchan[i].slot = i;
}
>>>mask and clear all interrupt vectors
writel(0x0, ACK_INT_MSK_REG(mbox->ipc));
writel(~0x0, ACK_INT_CLR_REG(mbox->ipc));
>>>判断中断使用poll方式还是中断方式
/* use interrupt for tx's ack */
if (of_find_property(node, "hi6220,mbox-tx-noirq", NULL))
mbox->tx_irq_mode = false;
else
mbox->tx_irq_mode = true;
if (mbox->tx_irq_mode)
mbox->controller.txdone_irq = true;
else {
mbox->controller.txdone_poll = true;
mbox->controller.txpoll_period = 5;
}
>>>注册控制器
err = mbox_controller_register(&mbox->controller);
>>>保存mbox设备数据到pdev->dev->driver_data
platform_set_drvdata(pdev, mbox);
hi6220_mbox_remove(struct platform_device *pdev)
>>>struct hi6220_mbox *mbox = platform_get_drvdata(pdev);
>>>mbox_controller_unregister(&mbox->controller);
6.2.1.3 中断处理流程
probe函数中注册中断，driver 收到remote的中断，读取数据调用mbox_chan_received_data将数据放到 client->rx_buffer中
static irqreturn_t hi6220_mbox_interrupt(int irq, void *p)
>>>读取中断状态(哪个子中断置位？？？)
state = readl(ACK_INT_STAT_REG(mbox->ipc));
>>> 查询每个子中断的状态并进行响应
while (state) {
>>>查询中断状态中的最高置1的位
intr_bit = __ffs(state);//
state &= (state - 1);
chan = mbox->irq_map_chan[intr_bit];//每个中断位对应一个中断通道
if (!chan) {
dev_warn(mbox->dev, "%s: unexpected irq vector %d
",
__func__, intr_bit);
continue;
}
mchan = chan->con_priv; //通道私有数据
if (mchan->dir == MBOX_TX) //若该通道（中断）为发送方向
mbox_chan_txdone(chan, 0);
else { //若该通道（中断）为接受方向
for (i = 0; i < MBOX_MSG_LEN; i++)
msg[i] = readl(mbox->base +MBOX_DATA_REG(mchan->slot) + i * 4);//读取数据
mbox_chan_received_data(chan, (void *)msg); //将数据交给数据接受函数进行处理
}
/* clear IRQ source */清中断
writel(BIT(mchan->ack_irq), ACK_INT_CLR_REG(mbox->ipc));
mbox_set_state(mbox, mchan->slot, MBOX_STATE_IDLE);
}
6.2.2 数据接收流程
数据接收是以中断的方式进行的。
hi6220_mbox_interrupt()
>>>for (i = 0; i < MBOX_MSG_LEN; i++)
msg[i] = readl(mbox->base +MBOX_DATA_REG(mchan->slot) + i * 4);//读取数据
>>>mbox_chan_received_data(chan, (void *)msg); //讲数据交给数据接受函数进行处理
>>>chan->cl->rx_callback(chan->cl, mssg); //上层client回调
6.2.3 数据发送流程
6.2.3.1 数据发送分为三种方式
中断方式，polling方式，ACK方式
#define TXDONE_BY_IRQ BIT(0) /* controller has remote RTR irq */
#define TXDONE_BY_POLL BIT(1) /* controller can read status of last TX */
#define TXDONE_BY_ACK BIT(2) /* S/W ACK recevied by Client ticks the TX */
6.2.3.2 数据发送的基本流程
1 获取mailbox的channel
1）申请通道时，client对象指定了自己的需求和能力；
2）在原子上下文中不能调用；
3）通道在一个client占用之后，没有释放之前，不能被其它client使用；
4）分配完成之后，任何此通道上接受的数据包将通过rx_callback传递到客户端
5）使用完成后调用mbox_free_channel 释放channel，这样别人就可以继续使用这个channel
void mbox_free_channel(struct mbox_chan *chan); /* may sleep */
struct mbox_chan *mbox_request_channel_byname(struct mbox_client *cl,const char *name);
struct mbox_chan *mbox_request_channel(struct mbox_client *cl, int index);
struct mbox_chan *mbox_request_channel(struct mbox_client *cl, int index)
函数功能：通过dts中配置的channel index申请通道
>>>of_parse_phandle_with_args(dev->of_node, "mboxes", "#mbox-cells", index, &spec)
>>>根据dts中配置的channel index获得mbox_chan
list_for_each_entry(mbox, &mbox_cons, node)
chan = mbox->of_xlate(mbox, &spec);
>>>初始化mbox
chan->msg_free = 0;
chan->msg_count = 0;
chan->active_req = NULL;
chan->cl = cl;
init_completion(&chan->tx_complete);
>>>启动通道
ret = chan->mbox->ops->startup(chan);
struct mbox_chan *mbox_request_channel_byname(struct mbox_client *cl,const char *name);
函数功能：通过channel name 申请通道，调用mbox_request_channel()函数来实现
2 使用mbox_send_message给controller发送数据
函数功能：在client提交数据到controller进而发送到目标处理器的过程中。
若client设置为tx_block，此函数调用只有在远程已经完成数据接受或tx_out（超时）才能返回；
若client设置为非block模式下，client的每个请求将被此API进行缓存，并返回一个非负数；
若client请求没有进入queue,将返回一个负数。
无论失败，还是成功，API将调用tx_done；
int mbox_send_message(struct mbox_chan *chan, void *mssg)
>>> t = add_to_rbuf(chan, mssg); //将要发送的msg发暂存到对应通道的rbuf中
>>>msg_submit(chan);
>>>data = chan->msg_data[idx];
>>>chan->cl->tx_prepare(chan->cl, data); //发到缓存
>>>err = chan->mbox->ops->send_data(chan, data); //发送数据 hi6220_mbox_send_data,
>>>mbox_set_state(mbox, slot, MBOX_STATE_TX);
>>>if (mbox->tx_irq_mode)
mbox_set_mode(mbox, slot, MBOX_ACK_IRQ);
>>>发送数据
for (i = 0; i < MBOX_MSG_LEN; i++)
writel(buf[i], mbox->base + MBOX_DATA_REG(slot) + i * 4);
>>>/* trigger remote request */
writel(BIT(mchan->dst_irq), DST_INT_RAW_REG(mbox->ipc));
等待中断。。。。。。。。。。
------------------------------------------------------
在中断服务函数中
发送完成中断到来----------->
>>>hi6220_mbox_interrupt
>>>mbox_chan_txdone(chan, 0);
>>>tx_tick(chan, r);
>>>msg_submit(chan);
>>>chan->cl->tx_done(chan->cl, mssg, r);
------------------------------------------------------
>>>若为polling方式下，启定时器
hrtimer_start(&chan->mbox->poll_hrt, 0, HRTIMER_MODE_REL);
>>>若为block形式的发送
>>>设置超时时间
wait = msecs_to_jiffies(3600000);//永不超时
wait = msecs_to_jiffies(chan->cl->tx_tout);
>>>阻塞等待超时或完成
ret = wait_for_completion_timeout(&chan->tx_complete, wait);
>>>若超时时间到
tx_tick(chan, t);
>>>chan->cl->tx_done(chan->cl, mssg, r);
>>>complete(&chan->tx_complete);
6.3 Mailbox Client驱动
以mailbox-test为例说明。
struct mbox_test_device {
struct device *dev;
void __iomem *tx_mmio;
void __iomem *rx_mmio;
struct mbox_chan *tx_channel;
struct mbox_chan *rx_channel;
char *rx_buffer;
char *signal;
char *message;
spinlock_t lock;
wait_queue_head_t waitq;
struct fasync_struct *async_queue;
};
6.3.1 Client 设备树相关的配置
Controller
----------
Required properties:
- compatible : Should be "st,stih407-mailbox"
- reg : Offset and length of the device's register set
- mbox-name : Name of the mailbox
- #mbox-cells: : Must be 2
<&phandle instance channel direction>
phandle : Label name of controller
instance : Instance number
channel : Channel number
Optional properties
- interrupts : Contains the IRQ line for a Rx mailbox
Example:
mailbox0: mailbox@0 {
compatible = "st,stih407-mailbox";
reg = <0x08f00000 0x1000>;
interrupts = <GIC_SPI 1 IRQ_TYPE_NONE>;
#mbox-cells = <2>;
mbox-name = "a9";
};
Client
------
Required properties:
- compatible : Many (See the client docs)
- reg : Shared (between Application and Remote) memory address
- mboxes : Standard property to specify a Mailbox (See ./mailbox.txt)
Cells must match 'mbox-cells' (See Controller docs above)
Optional properties
- mbox-names : Name given to channels seen in the 'mboxes' property.
Example:
mailbox_test {
compatible = "mailbox-test";
reg = <0x[shared_memory_address], [shared_memory_size]>;
mboxes = <&mailbox2 0 1>, <&mailbox0 2 1>;
mbox-names = "tx", "rx";
};
6.3.2 Client初始化
static struct platform_driver mbox_test_driver = {
.driver = {
.name = "mailbox_test",
.of_match_table = mbox_test_match,
},
.probe = mbox_test_probe,
.remove = mbox_test_remove,
};
module_platform_driver(mbox_test_driver);
static int mbox_test_probe(struct platform_device *pdev)
>>>tdev = devm_kzalloc(&pdev->dev, sizeof(*tdev), GFP_KERNEL);
>>>res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
>>>size = resource_size(res);
>>>tdev->tx_mmio = devm_ioremap_resource(&pdev->dev, res);
>>>申请通道
tdev->tx_channel = mbox_test_request_channel(pdev, "tx");
tdev->rx_channel = mbox_test_request_channel(pdev, "rx");
>>> client = devm_kzalloc(&pdev->dev, sizeof(*client), GFP_KERNEL);
>>> client->dev = &pdev->dev;
>>> client->rx_callback = mbox_test_receive_message;
>>> client->tx_prepare = mbox_test_prepare_message;
>>> client->tx_done = mbox_test_message_sent;
>>> client->tx_block = true;
>>> client->knows_txdone = false;
>>> client->tx_tout = 500;
>>> channel = mbox_request_channel_byname(client, name); //调用API申请通道
>>>platform_set_drvdata(pdev, tdev);
>>>spin_lock_init(&tdev->lock);
>>>tdev->rx_buffer = devm_kzalloc(&pdev->dev,
MBOX_MAX_MSG_LEN, GFP_KERNEL);
>>>ret = mbox_test_add_debugfs(pdev, tdev);
>>>init_waitqueue_head(&tdev->waitq);
static int mbox_test_remove(struct platform_device *pdev)
>>> debugfs_remove_recursive(root_debugfs_dir);
>>> mbox_free_channel(tdev->tx_channel);
>>> mbox_free_channel(tdev->rx_channel);
6.3.3 Client数据收发
数据接收（回调函数）
static void mbox_test_receive_message(struct mbox_client *client, void *message)
spin_lock_irqsave(&tdev->lock, flags);
if (tdev->rx_mmio) {
memcpy_fromio(tdev->rx_buffer, tdev->rx_mmio, MBOX_MAX_MSG_LEN);
} else if (message) {
memcpy(tdev->rx_buffer, message, MBOX_MAX_MSG_LEN);
}
mbox_data_ready = true;
spin_unlock_irqrestore(&tdev->lock, flags);
wake_up_interruptible(&tdev->waitq);
kill_fasync(&tdev->async_queue, SIGIO, POLL_IN);
数据发送
static void mbox_test_prepare_message(struct mbox_client *client, void *message)
{
struct mbox_test_device *tdev = dev_get_drvdata(client->dev);
if (tdev->tx_mmio) {
if (tdev->signal)
memcpy_toio(tdev->tx_mmio, tdev->message, MBOX_MAX_MSG_LEN);
else
memcpy_toio(tdev->tx_mmio, message, MBOX_MAX_MSG_LEN);
}
}
static void mbox_test_message_sent(struct mbox_client *client,
void *message, int r)
{
if (r)
dev_warn(client->dev,
"Client: Message could not be sent: %d
", r);
else
dev_info(client->dev,
"Client: Message sent
");
}
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版权声明：本文为CSDN博主「huofengfeihu」的原创文章，遵循CC 4.0 BY-SA版权协议，转载请附上原文出处链接及本声明。
原文链接：https://blog.csdn.net/u010961173/article/details/96422441