Re: OpenProtocol() giving me EFI_INVALID_PARAMETER

["Ethin Probst" <harlydavidsen@gmail.com>]

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?

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