Developing Games on Intel Graphics
If you are gaming on graphics integrated in your Intel Processor, this is the place for you! Find answers to your questions or post your issues with PC games
507 Discussions

Reading DPCD register data from remotely connected DP1.2 display

ELu11
Beginner
1,361 Views

Hi,

I am using below reference code in the CUI Doc v0.96 to read DPCD register data from a DP-VGA dongle which is connected to the downstream port of DP MST Hub (PC -> DP MST Hub -> DP-VGA dongle -> VGA monitor).

struct IGFX_DP_AUX_INFO

{

    enum IGFX_PORT_TYPES portType;

    struct IGFX_DP_RELATIVE_ADDRESS relativeAddress;

    unsigned long dwOpType;

    unsigned long dwSize;

    unsigned long dwAddress;

    unsigned char Data[132];

};

IGFX_DP_AUX_INFO InData;

DWORD dwError = 0;

ZeroMemory(&InData, sizeof(IGFX_DP_AUX_INFO));

InData.relativeAddress.ucTotalLinkCount = pDisplays->relativeAddress.ucTotalLinkCount;

InData.relativeAddress.ucAddress[0] = pDisplays->relativeAddress.ucAddress[0];

InData.portType = pDPTopology-> PortList[0];

InData.dwOpType = IGFX_REMOTE_AUX_READ;

InData.dwSize = 5;

InData.dwAddress = 0x500;    

hr = pCUIExternal8->GetDeviceData((GUID*)&IGFX_GET_SET_REMOTE_AUX_INFO_GUID, sizeof(InData), (BYTE*)&InData, &dwError);

I could see DP MST Hub reading 5 bytes DPCD register data from DP-VGA dongle at DPCD register address 0x500 by using DP AUX analyzer and received hr = OK from API call, however the reading back DPCD register data is not stored in the data buffer (InData.Data[]). InData.Data[0] - [131] has all "0" data.

Any comment to solve the issue would be very appreciated.

 

Thanks,

Eric Lu

NXP Semiconductors

0 Kudos
0 Replies
Reply