Re: Problem in EFI_BOOT_SERVICES.OpenProtocol()

[Amit kumar <akamit91@hotmail.com>]

Hello Andrew,


Thanks for quick reply and acknowledging my query.


Amit

________________________________
From: afish@apple.com <afish@apple.com> on behalf of Andrew Fish <afish@apple.com>
Sent: Thursday, June 1, 2017 10:59:03 PM
To: Amit kumar
Cc: edk2-devel@lists.01.org
Subject: Re: [edk2] Problem in EFI_BOOT_SERVICES.OpenProtocol()


> On Jun 1, 2017, at 10:13 AM, Amit kumar <akamit91@hotmail.com> wrote:
>
> Hello Andrew,
>
> As per UEFI Spec EFI_ALREADY_STARTED is treated as error code, thus PciIo (The Interface 3rd parameter ) should remain NULL.
> But after    OpenProtocol call even though Status = EFI_ALREADY_STARTED PciIo (The Interface 3rd parameter ) is getting modified and it not NULL anymore.
> Is this not a problem ?
>

Amit,

I agree it looks like the code will fill in the Interface and return EFI_ALREADY_STARTED. And that does seem to conflict with the section of the spec you quote. Good catch.

https://github.com/tianocore/edk2/blob/master/MdeModulePkg/Core/Dxe/Hand/Handle.c#L1097
  //
  // This is the protocol interface entry for this protocol
  //
  if (Attributes != EFI_OPEN_PROTOCOL_TEST_PROTOCOL) {
    *Interface = Prot->Interface;
  }
  Status = EFI_SUCCESS;

  ByDriver        = FALSE;
  Exclusive       = FALSE;
  for ( Link = Prot->OpenList.ForwardLink; Link != &Prot->OpenList; Link = Link->ForwardLink) {
    OpenData = CR (Link, OPEN_PROTOCOL_DATA, Link, OPEN_PROTOCOL_DATA_SIGNATURE);
    ExactMatch =  (BOOLEAN)((OpenData->AgentHandle == ImageHandle) &&
                            (OpenData->Attributes == Attributes)  &&
                            (OpenData->ControllerHandle == ControllerHandle));
    if ((OpenData->Attributes & EFI_OPEN_PROTOCOL_BY_DRIVER) != 0) {
      ByDriver = TRUE;
      if (ExactMatch) {
        Status = EFI_ALREADY_STARTED;
        goto Done;
      }
    }
    if ((OpenData->Attributes & EFI_OPEN_PROTOCOL_EXCLUSIVE) != 0) {
      Exclusive = TRUE;
    } else if (ExactMatch) {
      OpenData->OpenCount++;
      Status = EFI_SUCCESS;
      goto Done;
    }
  }

Thanks,

Andrew Fish

> Status = gBS->OpenProtocol (
>                  Controller,
>                  &gEfiPciIoProtocolGuid,
>                  (VOID **) &PciIo,
>                  This->DriverBindingHandle,
>                  Controller,
>                  EFI_OPEN_PROTOCOL_BY_DRIVER
>                  );
>
> ________________________________
> From: afish@apple.com <afish@apple.com> on behalf of Andrew Fish <afish@apple.com>
> Sent: Thursday, June 1, 2017 10:28:16 PM
> To: Amit kumar
> Cc: edk2-devel@lists.01.org
> Subject: Re: [edk2] Problem in EFI_BOOT_SERVICES.OpenProtocol()
>
>
>> On Jun 1, 2017, at 9:46 AM, Amit kumar <akamit91@hotmail.com> wrote:
>>
>> Hi,
>> I am trying to open PciIoProtocol and facing some issue.
>>
>> below is the code
>>
>> EFI_PCI_IO_PROTOCOL *PciIo=NULL;
>> EFI_STATUS                      Status;
>>
>> Status = gBS->OpenProtocol (
>>                 Controller,
>>                 &gEfiPciIoProtocolGuid,
>>                 (VOID **) &PciIo,
>>                 This->DriverBindingHandle,
>>                 Controller,
>>                 EFI_OPEN_PROTOCOL_BY_DRIVER
>>                 );
>>
>> it returns Status = EFI_ALREADY_STARTED, but PciIo is not NULL.
>> Is it not supposed to return PciIo as NULL ?
>> As per UEFI 2.6 Spec Section 6.3 page 182.
>>
>
> Amit,
>
> Look at the Status Codes Returned section at the end of that section.
>
> Attributes is BY_DRIVER and there is an item on the open list with an attribute of BY_DRIVER whose agent handle is the same as AgentHandle.
>
> Attributes is BY_DRIVER|EXCLUSIVE and there is an item on the open list with an attribute of BY_DRIVER|EXCLUSIVE whose agent handle is the same as AgentHandle.
>
> Thanks,
>
> Andrew Fish
>
>> There are a number of reasons that this function call can return an error. If an error is returned, then
>> AgentHandle, ControllerHandle, and Attributes are not added to the list of agents
>> consuming the protocol interface specified by Handle and Protocol, and Interface is
>> returned unmodified.
>>
>> Thanks And Regards
>> Amit
>> _______________________________________________
>> edk2-devel mailing list
>> edk2-devel@lists.01.org
>> https://lists.01.org/mailman/listinfo/edk2-devel
>
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