> On Jul 17, 2021, at 10:06 AM, Ethin Probst <harlydavidsen@gmail.com> wrote:
> 
> Okay, so I just tried dh -v 7EDE4C18 (that was the handle that I'm
> getting from `HandleBuffer()`) and it says "dh: Handle - '7EDE4C18'
> not found". So I'm definitely confused because that's what
> `HandleBuffer()` is getting me. Should I pre-allocate the buffer?
> 

Ethin,

The UEFI Shell `dh` command  UI uses handle numbers from 0 - N as hex digits. You have use these abstract values with the `dh` command. For example:  use `dh -v A1` to see the actual handle value for A1 (7EBA9598). You can search handles that contain a specific protocol...

Shell> dh -p PciIo
Handle dump by protocol 'PCIIO'
A1: PCIIO DevicePath(PciRoot(0x0)/Pci(0x0,0x0)) 
A2: PCIIO DevicePath(PciRoot(0x0)/Pci(0x1,0x0)) 
A3: PCIIO DevicePath(PciRoot(0x0)/Pci(0x2,0x0)) 
A4: PCIIO DevicePath(..0)/Pci(0x2,0x0)/Pci(0x0,0x0)) 
A5: PCIIO DevicePath(..0)/Pci(0x2,0x0)/Pci(0x1,0x0)) 
A6: PCIIO DevicePath(..0)/Pci(0x2,0x0)/Pci(0x2,0x0)) 
A7: PCIIO DevicePath(..0)/Pci(0x2,0x0)/Pci(0x3,0x0)) 
A8: PCIIO DevicePath(..0)/Pci(0x2,0x0)/Pci(0x4,0x0)) 
A9: PCIIO DevicePath(..0)/Pci(0x2,0x0)/Pci(0x5,0x0)) 
AA: PCIIO DevicePath(PciRoot(0x0)/Pci(0x1E,0x0)) 
AB: DiskIO BlockIO FA920010-6785-4941-B6EC-498C579F160A PCIIO DevicePath(..)/Pci(0x1E,0x0)/Pci(0x0,0x0)) 
AC: ISAACPI PCIIO DevicePath(PciRoot(0x0)/Pci(0x1F,0x0)) 
AD: PCIIO DevicePath(PciRoot(0x0)/Pci(0x1F,0x3)) 
Shell> dh -v A1
A1: 7EBA9598
PCIIO(7EBA8AA8)
  Segment #.....: 00
  Bus #.........: 00
  Device #......: 00
  Function #....: 00
  ROM Size......: 0
  ROM Location..: 00000000
  Vendor ID.....: 8086
  Device ID.....: 29C0
  Class Code....: 00 00 06
  Configuration Header :
       8680C029070000000000000600000000
       00000000000000000000000000000000
       000000000000000000000000F41A0011
       000000000000000000000000FF000000
DevicePath(7EBA9E18)
  PciRoot(0x0)/Pci(0x0,0x0)

Thanks,

Andrew Fish

> On 7/17/21, Ethin Probst <harlydavidsen@gmail.com> wrote:
>> I mean, possible... The code I'm using to initialize the handle buffer is
>> this:
>> 
>> ```C
>> EFI_STATUS EFIAPI UefiMain(IN EFI_HANDLE imageHandle, IN EFI_SYSTEM_TABLE*
>> st) {
>>  Print(L"Attempting to find USB IO protocol\n");
>>  UINTN numHandles = 0;
>>  UINTN i = 0;
>>  UINT32 UsbStatus = 0;
>>  EFI_HANDLE* handles = NULL;
>>  EFI_USB_IO_PROTOCOL* UsbIo = NULL;
>>  EFI_STATUS status = st->BootServices->LocateHandleBuffer(ByProtocol,
>> &gEfiUsbIoProtocolGuid, NULL, &numHandles, &handles);
>>  if (EFI_ERROR(status)) {
>>    Print(L"Cannot find any handles for USB devices, reason: %r\n",
>> status);
>>    return EFI_ABORTED;
>>  }
>>  Print(L"Found %d USB devices; enumerating\n", numHandles);
>>  for (; i < numHandles; ++i) {
>>    Print(L"Trying to open handle %d (%x)... ", i, handles[i]);
>>    status = st->BootServices->OpenProtocol(handles[i],
>> &gEfiUsbIoProtocolGuid, (void**)&UsbIo, imageHandle, NULL,
>> EFI_OPEN_PROTOCOL_EXCLUSIVE);
>>    if (EFI_ERROR(status)) {
>>      Print(L"%r, skipping\n", status);
>>      continue;
>>    }
>>    // ...
>> ```
>> I've done my best to follow SEI secure C coding standards, like
>> initializing all variables, regardless of type -- e.g. initializing
>> pointers to 0/NULL. But I will definitely try that idea.
>> 
>> On 7/17/21, Andrew Fish <afish@apple.com> wrote:
>>> 
>>> 
>>>> On Jul 17, 2021, at 9:41 AM, Ethin Probst <harlydavidsen@gmail.com>
>>>> wrote:
>>>> 
>>>> Hey all,
>>>> 
>>>> So my UsbAudio.efi app has hit a bit of a roadblock. This code:
>>>> 
>>>> ```C
>>>>   status = st->BootServices->OpenProtocol(handles[i],
>>>> &gEfiUsbIoProtocolGuid, (void**)&UsbIo, imageHandle, NULL,
>>>> EFI_OPEN_PROTOCOL_EXCLUSIVE);
>>>>   if (EFI_ERROR(status)) {
>>>>     Print(L"%r, skipping\n", status);
>>>>     continue;
>>>>   }
>>>> ```
>>> 
>>> How are you constructing handle[]? Could it have gotten stale? You could
>>> print out the value of handle[I] on the failure.
>>> 
>>> The contents of a handle are not defined, but the current implementation
>>> is
>>> a pointer to an IHANDLE internal data structure in the DXE Core. If you
>>> are
>>> at the UEFI Shell and you `dh -v <handleNum> it will show the <handleNum>
>>> and the value.
>>> 
>>> Shell> dh -v 98
>>> 98: 6d5CF18
>>> ….
>>> 
>>> I think you can `dh -p UsbIo’ to get the list of the UsbIo handles.
>>> 
>>> So you can poke around and see what is happening on that handle.
>>> 
>>> I guess the handle[] array could be getting corrupted? So you could check
>>> for that?
>>> 
>>> Thanks,
>>> 
>>> Andrew Fish
>>> 
>>>> Is giving me EFI_INVALID_PARAMETER and I don’t know why. I don't think
>>>> I'm violating any of its constraints, according to the specification,
>>>> and I haven't touched this code since it was written. It also happens
>>>> irregularly: sometimes it happens on the USB audio streaming device,
>>>> or if I have a device plugged in it might happen on that device, you
>>>> get the idea. But it doesn't consistently fail. Does anybody have any
>>>> idea what's going on?
>>>> 
>>>> --
>>>> Signed,
>>>> Ethin D. Probst
>>> 
>>> 
>> 
>> 
>> --
>> Signed,
>> Ethin D. Probst
>> 
> 
> 
> -- 
> Signed,
> Ethin D. Probst
> 
> 
> 
> 
>