本篇章主要介绍高通平台USB数据转发给modem流程。
一、图解port_bridge作用
port_bridge的功能是将从USB接受到的数据转发至SMD，该阶段在linux debug口上进行排查，通过分析port_bridge进程的状态及执行log，定位问题发生位置。
二、port_bridge入口分析
目录：apps_proc/data/port-bridge/port_bridge.c
int main() { pthread_t mdm_thread, usb_thread; thread_info_t mdm_info, usb_info; /* MDM -> USB info object */ mdm_info.from_fd = &mdm_fd; mdm_info.to_fd = &usb_fd; mdm_info.to_file_path = targetinfo.usb_chardev; mdm_info.from_file_path = targetinfo.mdm_chardev; mdm_info.to_mutex = &usb_mutex; mdm_info.from_mutex = &mdm_mutex; /* USB -> MDM info object */ usb_info.from_fd = &usb_fd; usb_info.to_fd = &mdm_fd; usb_info.from_file_path = targetinfo.usb_chardev; usb_info.to_file_path = targetinfo.mdm_chardev; usb_info.to_mutex = &mdm_mutex; usb_info.from_mutex = &usb_mutex; pthread_create(&mdm_thread, NULL, targetinfo.mdm_handler, &mdm_info); pthread_create(&usb_thread, NULL, usb_to_modem_bridge, &usb_info); pthread_join(mdm_thread, NULL); pthread_join(usb_thread, NULL); }
三、usb_to_modem_bridge线程
USB -> MDM这里操作的 glink_pkt
void* usb_to_modem_bridge(void* thread_info) { thread_info_t tinfo = *((thread_info_t*)thread_info); while (1) { /* ####### OPEN THE USB FILE ####### */ if (*tinfo.from_fd < 0) { temp_fd = open(tinfo.from_file_path, O_RDWR); /* Custom blocking open */ } while (glink_rx_intent_count < GLINK_RX_INTENT_MIN) { unsigned int rx_packet_max_size = MAX_MSG_SIZE; LOGI("Queuing RX Intent for '%s'\n", tinfo.from_file_path); PB_PTHREAD_MUTEX_LOCK(tinfo.from_mutex, tinfo.from_file_path); ret = ioctl(*tinfo.from_fd, GLINK_PKT_IOCTL_QUEUE_RX_INTENT, &rx_packet_max_size); PB_PTHREAD_MUTEX_UNLOCK(tinfo.from_mutex, tinfo.from_file_path); if (ret) { LOGE("Error queuing RX intent=%d\n", ret); exit(1); } glink_rx_intent_count++; } // At this point it's open, so poll for anything we need to do pollinfo.revents = 0; LOGI("Attempting to poll '%s'...\n", tinfo.from_file_path); ret = poll(&pollinfo, 1, -1); // -1 timeout specifies infinite block (default linux behavior) LOGR(ret, "poll on '%s' returned %i\n", tinfo.from_file_path, ret); }
四、/dev/at_mdm0处理AT指令
前面分析到port_bridge进程会将从PC发过来的数据写入到/dev/at_mdm0中，那么这个过程又是怎样的呢？/dev/at_mdm0驱动代码位于drivers/soc/qcom/glink_pkt.c，写入的时候最终会调用glink_pkt_write, glink_pkt_write的流程如下:
ssize_t glink_pkt_write(struct file *file, const char __user *buf, size_t count, loff_t *ppos) { struct glink_pkt_device *gpdev = file->private_data; void *kbuf; int ret; gpdev = file->private_data; if (!gpdev || refcount_read(&gpdev->refcount) == 1) { GLINK_PKT_ERR("invalid device handle\n"); return -EINVAL; } GLINK_PKT_INFO("begin to %s buffer_size %zu\n", gpdev->ch_name, count); kbuf = memdup_user(buf, count); if (IS_ERR(kbuf)) return PTR_ERR(kbuf); if (mutex_lock_interruptible(&gpdev->lock)) { ret = -ERESTARTSYS; goto free_kbuf; } if (!completion_done(&gpdev->ch_open) || !gpdev->rpdev) { GLINK_PKT_ERR("%s channel in reset\n", gpdev->ch_name); ret = -ENETRESET; goto unlock_ch; } if (file->f_flags & O_NONBLOCK) ret = rpmsg_trysend(gpdev->rpdev->ept, kbuf, count); else ret = rpmsg_send(gpdev->rpdev->ept, kbuf, count); unlock_ch: mutex_unlock(&gpdev->lock); free_kbuf: kfree(kbuf); GLINK_PKT_INFO("finish to %s ret %d\n", gpdev->ch_name, ret); return ret < 0 ? ret : count; }
