Does EC200A needs URB_ZERO_PACKET mechanisam?

Technical Subjects Driver
1

I am doing kernel changes on linux-6.1. Modem EC200A is already defined in this version, but your Linux_USB_Driver_User_Guide guide states that I should make this change in option.c driver:

    if (dir == USB_DIR_OUT) {
            struct usb_device_descriptor *desc = &serial->dev->descriptor;
            if (desc->idVendor == cpu_to_le16(0x2C7C))
                    urb->transfer_flags |= URB_ZERO_PACKET;
    }

This was relevant by my opinion before introducing ZLP flag. But line which defines modem does not use ZLP flag.

{ USB_DEVICE_AND_INTERFACE_INFO(QUECTEL_VENDOR_ID, QUECTEL_PRODUCT_EC200U, 0xff, 0, 0) }

Is this correct?

Because in usb_wwan.c I will never pass this condition

    if (intfdata->use_zlp && dir == USB_DIR_OUT)
            urb->transfer_flags |= URB_ZERO_PACKET

Are you sending zero packets at the end of bulk transfer or not (because some modems do that some does not), should I integrate change mention in Linux USB Driver?

Greetings

2

What’s the Linux kernel and which Linux CPU you are using now?
It is better to add the URB_ZERO_PACKET

But for linux kernel before the linux 4.x, it might not support the USB ZERO packet feature.

3