doc/topics/sdk/usb/usb-gadget_device.html

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                        <div class=" wh_topic_content body "><main role="main"><article class="- topic/topic concept/concept topic concept" role="article" aria-labelledby="ariaid-title1"><span class="edit-link" style="font-size:12px; opacity:0.6; text-align:right; vertical-align:middle"><a target="_blank" href="http://172.16.35.88/tasks/jdssno1uvvbf2mltu9kb9v3if05d5gopuakboe8hlud18rma/edit/F:/aicdita/aicdita-cn/topics/sdk/usb/usb-gadget_device.dita">Edit online</a></span><h1 class="- topic/title title topictitle1" id="ariaid-title1">Gadget Device</h1><div class="date inPage">31 Jan 2024</div><div style="color: gray;">
                    Read time: 10 minute(s)
                </div><div class="- topic/body concept/conbody body conbody"><div class="- topic/p p" data-ofbid="d336238e22__20250121171845">上一节说过 Gadget Device 由 UDC Driver
            创建。<pre class="+ topic/pre pr-d/codeblock pre codeblock language-c" id="usb_gadget_device__codeblock_rrv_zqz_21c" data-ofbid="usb_gadget_device__codeblock_rrv_zqz_21c">dwc2_driver_probe() → usb_add_gadget_udc() → usb_add_gadget_udc_release() → usb_add_gadget()</pre></div><p class="- topic/p p" data-ofbid="d336238e26__20250121171845">Gadget Device 的主要作用是提供了 Endpoint 资源，供 Function Layer 使用标准的 Gadget API 来进行访问。</p><section class="- topic/section section" id="usb_gadget_device__section_uq1_zqz_21c" data-ofbid="usb_gadget_device__section_uq1_zqz_21c"><h2 class="- topic/title title sectiontitle">Endpoint Alloc</h2>
            
            <p class="- topic/p p" data-ofbid="d336238e33__20250121171845">UDC Driver 在调用 usb_add_gadget_udc() 注册 Gadget Device 之前，初始化了 Gadget 的 Endpoint
                资源链表：</p>
            <pre class="+ topic/pre pr-d/codeblock pre codeblock language-c" id="usb_gadget_device__pre_vq1_zqz_21c" data-ofbid="usb_gadget_device__pre_vq1_zqz_21c">dwc2_driver_probe() → dwc2_gadget_init():

<strong class="hl-keyword">int</strong> dwc2_gadget_init(<strong class="hl-keyword">struct</strong> dwc2_hsotg *hsotg)
{

    <em class="hl-comment">/* (1) 初始化 Gadget Device 的 Endpoint 资源链表为空  */</em>
    INIT_LIST_HEAD(&amp;hsotg-&gt;gadget.ep_list);
    hsotg-&gt;gadget.ep0 = &amp;hsotg-&gt;eps_out[<span class="hl-number">0</span>]-&gt;ep;


    <em class="hl-comment">/* initialise the endpoints now the core has been initialised */</em>
    <em class="hl-comment">/* (2) 初始化 UDC 拥有的 Endpoint，加入到 Gadget Device 的 Endpoint 资源链表中 */</em>
    <strong class="hl-keyword">for</strong> (epnum = <span class="hl-number">0</span>; epnum &lt; hsotg-&gt;num_of_eps; epnum++) {
        <strong class="hl-keyword">if</strong> (hsotg-&gt;eps_in[epnum])
            dwc2_hsotg_initep(hsotg, hsotg-&gt;eps_in[epnum],
                    epnum, <span class="hl-number">1</span>);
        <strong class="hl-keyword">if</strong> (hsotg-&gt;eps_out[epnum])
            dwc2_hsotg_initep(hsotg, hsotg-&gt;eps_out[epnum],
                    epnum, <span class="hl-number">0</span>);
    }

}

↓

<strong class="hl-keyword">static</strong> <strong class="hl-keyword">void</strong> dwc2_hsotg_initep(<strong class="hl-keyword">struct</strong> dwc2_hsotg *hsotg,
                <strong class="hl-keyword">struct</strong> dwc2_hsotg_ep *hs_ep,
                    <strong class="hl-keyword">int</strong> epnum,
                    bool dir_in)
{


    INIT_LIST_HEAD(&amp;hs_ep-&gt;queue);
    INIT_LIST_HEAD(&amp;hs_ep-&gt;ep.ep_list);

    <em class="hl-comment">/* add to the list of endpoints known by the gadget driver */</em>
    <em class="hl-comment">/* (2.1) UDC 中除了 endpoint0 以外，其他的 endpoint 都加入到 Device  的 Endpoint 资源链表 `gadget.ep_list` 中
            endpoint0 的操作由 UDC 驱动自己来处理
    */</em>
    <strong class="hl-keyword">if</strong> (epnum)
        list_add_tail(&amp;hs_ep-&gt;ep.ep_list, &amp;hsotg-&gt;gadget.ep_list);

    <em class="hl-comment">/* (2.2) 初始化 endpoint 的结构体成员 */</em>
    hs_ep-&gt;parent = hsotg;
    hs_ep-&gt;ep.name = hs_ep-&gt;name;

    <strong class="hl-keyword">if</strong> (hsotg-&gt;params.speed == DWC2_SPEED_PARAM_LOW)
        usb_ep_set_maxpacket_limit(&amp;hs_ep-&gt;ep, <span class="hl-number">8</span>);
    <strong class="hl-keyword">else</strong>
        usb_ep_set_maxpacket_limit(&amp;hs_ep-&gt;ep,
                    epnum ? <span class="hl-number">1024</span> : EP0_MPS_LIMIT);

    <em class="hl-comment">/* (2.3) endpoint 最重要的结构体成员，endpoint 操作函数集
        endpoint 的相关操作最后调用到这些函数上
    */</em>
    hs_ep-&gt;ep.ops = &amp;dwc2_hsotg_ep_ops;

    <strong class="hl-keyword">if</strong> (epnum == <span class="hl-number">0</span>) {
        hs_ep-&gt;ep.caps.type_control = true;
    } <strong class="hl-keyword">else</strong> {
        <strong class="hl-keyword">if</strong> (hsotg-&gt;params.speed != DWC2_SPEED_PARAM_LOW) {
            hs_ep-&gt;ep.caps.type_iso = true;
            hs_ep-&gt;ep.caps.type_bulk = true;
        }
        hs_ep-&gt;ep.caps.type_int = true;
    }

    <strong class="hl-keyword">if</strong> (dir_in)
        hs_ep-&gt;ep.caps.dir_in = true;
    <strong class="hl-keyword">else</strong>
        hs_ep-&gt;ep.caps.dir_out = true;

}
</pre>
            <p class="- topic/p p" data-ofbid="d336238e39__20250121171845">Gadget Device 准备好了 Endpoint 资源链表以后，通过 usb_add_gadget_udc() 注册。这样就可以 Function Layer
                就可以通过调用 Gadget Api 来动态分配 Endpoint 了。例如：</p>
            <pre class="+ topic/pre pr-d/codeblock pre codeblock language-c" id="usb_gadget_device__pre_wq1_zqz_21c" data-ofbid="usb_gadget_device__pre_wq1_zqz_21c"><strong class="hl-keyword">static</strong> <strong class="hl-keyword">int</strong>
acm_bind(<strong class="hl-keyword">struct</strong> usb_configuration *c, <strong class="hl-keyword">struct</strong> usb_function *f)
{

    <em class="hl-comment">/* allocate instance-specific endpoints */</em>
    <em class="hl-comment">/* (1) 从 Gadget Device 中分配一个 in endpoint */</em>
    ep = usb_ep_autoconfig(cdev-&gt;gadget, &amp;acm_fs_in_desc);
    <strong class="hl-keyword">if</strong> (!ep)
        <strong class="hl-keyword">goto</strong> fail;
    acm-&gt;port.in = ep;

    <em class="hl-comment">/* (2) 从 Gadget Device 中分配一个 out endpoint */</em>
    ep = usb_ep_autoconfig(cdev-&gt;gadget, &amp;acm_fs_out_desc);
    <strong class="hl-keyword">if</strong> (!ep)
        <strong class="hl-keyword">goto</strong> fail;
    acm-&gt;port.out = ep;

    <em class="hl-comment">/* (3) 从 Gadget Device 中分配一个 notify endpoint */</em>
    ep = usb_ep_autoconfig(cdev-&gt;gadget, &amp;acm_fs_notify_desc);
    <strong class="hl-keyword">if</strong> (!ep)
        <strong class="hl-keyword">goto</strong> fail;
    acm-&gt;notify = ep;

}
</pre>
            <p class="- topic/p p" data-ofbid="d336238e46__20250121171845">其中通过 usb_ep_autoconfig() 函数从 Gadget Device 的 Endpoint 资源链表中分配空闲的 endpoint:</p>
            <pre class="+ topic/pre pr-d/codeblock pre codeblock language-c" id="usb_gadget_device__pre_xq1_zqz_21c" data-ofbid="usb_gadget_device__pre_xq1_zqz_21c">drivers\usb\gadget\function\f_acm.c:

usb_ep_autoconfig() → usb_ep_autoconfig_ss():

<strong class="hl-keyword">struct</strong> usb_ep *usb_ep_autoconfig_ss(
    <strong class="hl-keyword">struct</strong> usb_gadget               *gadget,
    <strong class="hl-keyword">struct</strong> usb_endpoint_descriptor  *desc,
    <strong class="hl-keyword">struct</strong> usb_ss_ep_comp_descriptor *ep_comp
)
{
    <strong class="hl-keyword">struct</strong> usb_ep   *ep;

    <strong class="hl-keyword">if</strong> (gadget-&gt;ops-&gt;match_ep) {
        ep = gadget-&gt;ops-&gt;match_ep(gadget, desc, ep_comp);
        <strong class="hl-keyword">if</strong> (ep)
            <strong class="hl-keyword">goto</strong> found_ep;
    }

    <em class="hl-comment">/* Second, look at endpoints until an unclaimed one looks usable */</em>
    <em class="hl-comment">/* (1) 从 Gadget Device 的 Endpoint 资源链表中查找一个空闲的(ep-&gt;claimed 为空) 且符合要求的 endpoint  */</em>
    list_for_each_entry (ep, &amp;gadget-&gt;ep_list, ep_list) {
        <strong class="hl-keyword">if</strong> (usb_gadget_ep_match_desc(gadget, ep, desc, ep_comp))
            <strong class="hl-keyword">goto</strong> found_ep;
    }

    <em class="hl-comment">/* Fail */</em>
    <strong class="hl-keyword">return</strong> NULL;
found_ep:

    ...

    ep-&gt;address = desc-&gt;bEndpointAddress;
    ep-&gt;desc = NULL;
    ep-&gt;comp_desc = NULL;
    <em class="hl-comment">/* (2) 设置 endpoint 为已分配 */</em>
    ep-&gt;claimed = true;
    <strong class="hl-keyword">return</strong> ep;
}
</pre>
        </section><section class="- topic/section section" id="usb_gadget_device__section_yq1_zqz_21c" data-ofbid="usb_gadget_device__section_yq1_zqz_21c"><h2 class="- topic/title title sectiontitle">EndPoint Access</h2>
            
            <p class="- topic/p p" data-ofbid="d336238e57__20250121171845">Gadget Device 不仅仅为 Gadget Api 提供了分配 endpoint 的支持，还支持对 endpoint 收发数据的底层支持。在上一节的
                endpoint 初始化时，就已经设置 endpoint 的操作函数集 <code class="+ topic/ph pr-d/codeph ph codeph">dwc2_hsotg_ep_ops</code> ：</p>
            <pre class="+ topic/pre pr-d/codeblock pre codeblock language-c" id="usb_gadget_device__pre_zq1_zqz_21c" data-ofbid="usb_gadget_device__pre_zq1_zqz_21c">dwc2_driver_probe() → dwc2_gadget_init() → dwc2_hsotg_initep():

<strong class="hl-keyword">static</strong> <strong class="hl-keyword">void</strong> dwc2_hsotg_initep(<strong class="hl-keyword">struct</strong> dwc2_hsotg *hsotg,
                <strong class="hl-keyword">struct</strong> dwc2_hsotg_ep *hs_ep,
                    <strong class="hl-keyword">int</strong> epnum,
                    bool dir_in)
{

    <em class="hl-comment">/* (2.3) endpoint 最重要的结构体成员，endpoint 操作函数集
        endpoint 的相关操作最后调用到这些函数上
    */</em>
    hs_ep-&gt;ep.ops = &amp;dwc2_hsotg_ep_ops;

}

↓

<strong class="hl-keyword">static</strong> <strong class="hl-keyword">const</strong> <strong class="hl-keyword">struct</strong> usb_ep_ops dwc2_hsotg_ep_ops = {
    .enable         = dwc2_hsotg_ep_enable,
    .disable        = dwc2_hsotg_ep_disable_lock,
    .alloc_request  = dwc2_hsotg_ep_alloc_request,
    .free_request   = dwc2_hsotg_ep_free_request,
    .queue          = dwc2_hsotg_ep_queue_lock,
    .dequeue        = dwc2_hsotg_ep_dequeue,
    .set_halt       = dwc2_hsotg_ep_sethalt_lock,
    <em class="hl-comment">/* note, don't believe we have any call for the fifo routines */</em>
};
</pre>
            <p class="- topic/p p" data-ofbid="d336238e66__20250121171845">Gadget Api 提供了以下接口来操作 endpoint 读写数据。在 Host 侧对 endpoint 进行一次操作请求的数据结构是 <code class="+ topic/ph pr-d/codeph ph codeph">struct
                    urb</code> ，而在 Device 侧也有类似的数据结构称为 <code class="+ topic/ph pr-d/codeph ph codeph">struct usb_request</code> ，对
                endpoint 的数据读写就是围绕 <code class="+ topic/ph pr-d/codeph ph codeph">struct usb_request</code> 展开的：</p>
            <pre class="+ topic/pre pr-d/codeblock pre codeblock language-c" id="usb_gadget_device__pre_ar1_zqz_21c" data-ofbid="usb_gadget_device__pre_ar1_zqz_21c">drivers\usb\gadget\function\f_acm.c:

<strong class="hl-keyword">static</strong> <strong class="hl-keyword">int</strong> acm_cdc_notify(<strong class="hl-keyword">struct</strong> f_acm *acm, u8 type, u16 value,
        <strong class="hl-keyword">void</strong> *data, <strong class="hl-keyword">unsigned</strong> length)
{
    <strong class="hl-keyword">struct</strong> usb_ep                   *ep = acm-&gt;notify;
    <strong class="hl-keyword">struct</strong> usb_request              *req;
    <strong class="hl-keyword">struct</strong> usb_cdc_notification     *notify;
    <strong class="hl-keyword">const</strong> <strong class="hl-keyword">unsigned</strong>                  len = <strong class="hl-keyword">sizeof</strong>(*notify) + length;
    <strong class="hl-keyword">void</strong>                            *buf;
    <strong class="hl-keyword">int</strong>                             status;

    <em class="hl-comment">/* (1) 初始化 `struct usb_request` 数据结构 */</em>
    req = acm-&gt;notify_req;
    acm-&gt;notify_req = NULL;
    acm-&gt;pending = false;

    req-&gt;length = len;
    notify = req-&gt;buf;
    buf = notify + <span class="hl-number">1</span>;

    notify-&gt;bmRequestType = USB_DIR_IN | USB_TYPE_CLASS
            | USB_RECIP_INTERFACE;
    notify-&gt;bNotificationType = type;
    notify-&gt;wValue = cpu_to_le16(value);
    notify-&gt;wIndex = cpu_to_le16(acm-&gt;ctrl_id);
    notify-&gt;wLength = cpu_to_le16(length);
    memcpy(buf, data, length);

    <em class="hl-comment">/* ep_queue() can complete immediately if it fills the fifo... */</em>
    spin_unlock(&amp;acm-&gt;lock);
    <em class="hl-comment">/* (2) 提交 `usb_request` 请求到 endpoint 处理队列中 */</em>
    status = usb_ep_queue(ep, req, GFP_ATOMIC);
    spin_lock(&amp;acm-&gt;lock);

}
</pre>
            <p class="- topic/p p" data-ofbid="d336238e82__20250121171845">其中 usb_ep_queue() 函数就会调用 endpoint 的操作函数集 <code class="+ topic/ph pr-d/codeph ph codeph">dwc2_hsotg_ep_ops</code> 中的
                    <code class="+ topic/ph pr-d/codeph ph codeph">.queue</code> 函数：</p>
            <pre class="+ topic/pre pr-d/codeblock pre codeblock language-c" id="usb_gadget_device__pre_br1_zqz_21c" data-ofbid="usb_gadget_device__pre_br1_zqz_21c"><strong class="hl-keyword">int</strong> usb_ep_queue(<strong class="hl-keyword">struct</strong> usb_ep *ep,
                <strong class="hl-keyword">struct</strong> usb_request *req, gfp_t gfp_flags)
{
    <strong class="hl-keyword">int</strong> ret = <span class="hl-number">0</span>;

    <strong class="hl-keyword">if</strong> (WARN_ON_ONCE(!ep-&gt;enabled &amp;&amp; ep-&gt;address)) {
        ret = -ESHUTDOWN;
        <strong class="hl-keyword">goto</strong> out;
    }

    <em class="hl-comment">/* (1) 实际调用 dwc2_hsotg_ep_queue_lock() */</em>
    ret = ep-&gt;ops-&gt;queue(ep, req, gfp_flags);

out:
    trace_usb_ep_queue(ep, req, ret);

    <strong class="hl-keyword">return</strong> ret;
}
</pre>
        </section><section class="- topic/section section" id="usb_gadget_device__section_cr1_zqz_21c" data-ofbid="usb_gadget_device__section_cr1_zqz_21c"><h2 class="- topic/title title sectiontitle">UDC Control</h2>
            
            <p class="- topic/p p" data-ofbid="d336238e99__20250121171845">Gadget Device 还提供了 UDC 层级的一些操作函数，UDC Driver 在调用 usb_add_gadget_udc() 注册 Gadget Device
                之前，初始化了 Gadget 的 操作函数集：</p>
            <pre class="+ topic/pre pr-d/codeblock pre codeblock language-c" id="usb_gadget_device__pre_dr1_zqz_21c" data-ofbid="usb_gadget_device__pre_dr1_zqz_21c">dwc2_driver_probe() → dwc2_gadget_init():

<strong class="hl-keyword">int</strong> dwc2_gadget_init(<strong class="hl-keyword">struct</strong> dwc2_hsotg *hsotg)
{

    hsotg-&gt;gadget.max_speed = USB_SPEED_HIGH;
    <em class="hl-comment">/* (1) 初始化 Gadget Device 的操作函数集  */</em>
    hsotg-&gt;gadget.ops = &amp;dwc2_hsotg_gadget_ops;
    hsotg-&gt;gadget.name = dev_name(dev);
    hsotg-&gt;remote_wakeup_allowed = <span class="hl-number">0</span>;

}

↓

<strong class="hl-keyword">static</strong> <strong class="hl-keyword">const</strong> <strong class="hl-keyword">struct</strong> usb_gadget_ops dwc2_hsotg_gadget_ops = {
    .get_frame      = dwc2_hsotg_gadget_getframe,
    .set_selfpowered        = dwc2_hsotg_set_selfpowered,
    .udc_start              = dwc2_hsotg_udc_start,
    .udc_stop               = dwc2_hsotg_udc_stop,
    .pullup                 = dwc2_hsotg_pullup,
    .vbus_session           = dwc2_hsotg_vbus_session,
    .vbus_draw              = dwc2_hsotg_vbus_draw,
};
</pre>
            <p class="- topic/p p" data-ofbid="d336238e105__20250121171845">Gadget Api 提供了一些内部函数来调用：</p>
            <pre class="+ topic/pre pr-d/codeblock pre codeblock language-c" id="usb_gadget_device__pre_er1_zqz_21c" data-ofbid="usb_gadget_device__pre_er1_zqz_21c"><strong class="hl-keyword">static</strong> <strong class="hl-keyword">inline</strong> <strong class="hl-keyword">int</strong> usb_gadget_udc_start(<strong class="hl-keyword">struct</strong> usb_udc *udc)
{
    <strong class="hl-keyword">return</strong> udc-&gt;gadget-&gt;ops-&gt;udc_start(udc-&gt;gadget, udc-&gt;driver);
}

<strong class="hl-keyword">static</strong> <strong class="hl-keyword">inline</strong> <strong class="hl-keyword">void</strong> usb_gadget_udc_stop(<strong class="hl-keyword">struct</strong> usb_udc *udc)
{
    udc-&gt;gadget-&gt;ops-&gt;udc_stop(udc-&gt;gadget);
}

<strong class="hl-keyword">static</strong> <strong class="hl-keyword">inline</strong> <strong class="hl-keyword">void</strong> usb_gadget_udc_set_speed(<strong class="hl-keyword">struct</strong> usb_udc *udc,
                        <strong class="hl-keyword">enum</strong> usb_device_speed speed)
{
    <strong class="hl-keyword">if</strong> (udc-&gt;gadget-&gt;ops-&gt;udc_set_speed) {
        <strong class="hl-keyword">enum</strong> usb_device_speed s;

        s = min(speed, udc-&gt;gadget-&gt;max_speed);
        udc-&gt;gadget-&gt;ops-&gt;udc_set_speed(udc-&gt;gadget, s);
    }
}

<strong class="hl-keyword">int</strong> usb_gadget_connect(<strong class="hl-keyword">struct</strong> usb_gadget *gadget)
{
    <strong class="hl-keyword">int</strong> ret = <span class="hl-number">0</span>;

    <strong class="hl-keyword">if</strong> (!gadget-&gt;ops-&gt;pullup) {
        ret = -EOPNOTSUPP;
        <strong class="hl-keyword">goto</strong> out;
    }

    <strong class="hl-keyword">if</strong> (gadget-&gt;deactivated) {
        <em class="hl-comment">/*
        * If gadget is deactivated we only save new state.
        * Gadget will be connected automatically after activation.
        */</em>
        gadget-&gt;connected = true;
        <strong class="hl-keyword">goto</strong> out;
    }

    ret = gadget-&gt;ops-&gt;pullup(gadget, <span class="hl-number">1</span>);
    <strong class="hl-keyword">if</strong> (!ret)
        gadget-&gt;connected = <span class="hl-number">1</span>;

out:
    trace_usb_gadget_connect(gadget, ret);

    <strong class="hl-keyword">return</strong> ret;
}

<strong class="hl-keyword">int</strong> usb_gadget_disconnect(<strong class="hl-keyword">struct</strong> usb_gadget *gadget)
{
    <strong class="hl-keyword">int</strong> ret = <span class="hl-number">0</span>;

    <strong class="hl-keyword">if</strong> (!gadget-&gt;ops-&gt;pullup) {
        ret = -EOPNOTSUPP;
        <strong class="hl-keyword">goto</strong> out;
    }

    <strong class="hl-keyword">if</strong> (!gadget-&gt;connected)
        <strong class="hl-keyword">goto</strong> out;

    <strong class="hl-keyword">if</strong> (gadget-&gt;deactivated) {
        <em class="hl-comment">/*
        * If gadget is deactivated we only save new state.
        * Gadget will stay disconnected after activation.
        */</em>
        gadget-&gt;connected = false;
        <strong class="hl-keyword">goto</strong> out;
    }

    ret = gadget-&gt;ops-&gt;pullup(gadget, <span class="hl-number">0</span>);
    <strong class="hl-keyword">if</strong> (!ret) {
        gadget-&gt;connected = <span class="hl-number">0</span>;
        gadget-&gt;udc-&gt;driver-&gt;disconnect(gadget);
    }

out:
    trace_usb_gadget_disconnect(gadget, ret);

    <strong class="hl-keyword">return</strong> ret;
}</pre>
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