kr return -536854449 error

[WadeZhao23]

First, Thanks to the good repo.
I use the demo to send a command to USB device.
But the kr is -536854449.
`func getStatus() throws -> [UInt8] {
//Getting device interface from our pointer
guard let deviceInterface = self.deviceInfo.deviceInterfacePtrPtr?.pointee?.pointee else {
throw STM32DeviceError.DeviceInterfaceNotFound
}

    var kr:Int32 = 0
    let length:Int = 2
    var requestPtr:[UInt8] = [UInt8](repeating: 0, count: length)
    // Creating request
    var request = IOUSBDevRequest(bmRequestType: 161,
                                  bRequest: STM32REQUEST.DNLOAD.rawValue,
                                  wValue: 0,
                                  wIndex: 0,
                                  wLength: UInt16(length),
                                  pData: &requestPtr,
                                  wLenDone: 255)
    
    kr = deviceInterface.DeviceRequest(self.deviceInfo.deviceInterfacePtrPtr, &request)
    
    if (kr != kIOReturnSuccess) {
        throw STM32DeviceError.RequestError(desc: "Get device status request error: \(kr)")
    }
    
    return requestPtr
}`

[Arti3DPlayer]

What usb device are you using ? You should use bRequest, bmRequestType according to your usb device specs

[WadeZhao23]

What usb device are you using ? You should use bRequest, bmRequestType according to your usb device specs

OK，Thanks for your reply.
I am not familiar with USB device, so I met this stupid issue.

[gioele-santi]

Hi, I am facing similar problems and found out this is the way to read kernel return errors.

let systemError = String(format:"%02X", ((kr >> 26) & 0x3f))
let subError =  String(format:"%02X", ((kr >> 14) & 0xfff))
let codeError = String(format:"%02X",  ( kr & 0x3fff))

Meaning of errors for system and subsystem are in this header: https://opensource.apple.com/source/xnu/xnu-201/iokit/IOKit/
While USB errors are in this one:
https://opensource.apple.com/source/IOUSBFamily/IOUSBFamily-402.4.1/IOUSBFamily/Headers/USB.h.auto.html

[gioele-santi]

I am trying to understand better how the IOKit for USB works but it is very hard to find documentation (I am trying to send a custom data packet to an USB sensor that appears as a STM32 Mass Storage device). I am looking for device docs but it would be nice to understand the name of the variables. eg: What does the b and bm stand for in bRequest and bmRequestType? Do you know? Or maybe there's some kind of documentation you can suggest me?

[Arti3DPlayer]

I am trying to understand better how the IOKit for USB works but it is very hard to find documentation (I am trying to send a custom data packet to an USB sensor that appears as a STM32 Mass Storage device). I am looking for device docs but it would be nice to understand the name of the variables. eg: What does the b and bm stand for in bRequest and bmRequestType? Do you know? Or maybe there's some kind of documentation you can suggest me?

only on apple: https://developer.apple.com/library/archive/documentation/DeviceDrivers/Conceptual/IOKitFundamentals/Introduction/Introduction.html#//apple_ref/doc/uid/TP0000011