Accessing PCI video graphics card registers issue.

• Subject: Accessing PCI video graphics card registers issue.
• From: "rohit dhamija" <email@hidden>
• Date: Mon, 14 May 2007 17:48:12 +0530
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Dear all,

I have developed a kernel extension module for a monitor calibration
tool. The prime responsibilty of this module is to communicate to
graphics card which in turn communicates to the monitor through i2c
communication.

Video graphics card have set of registers for i2c communication - data
and clock. I need to communicate with a particular card, (ATI Rage 128
pro DVI) card but I do not have the base offsets and masking values
for the same.

So my query is to "how to find base offsets of i2c in a video graphics card ?"

Below is one of the method I planned to find the i2c data and clock
offsets and want your expert comments for the same. I would be
thankful if you could please review this idea and if possible share
some better alternate ideas

///////////////////////////////

Step 1)  MAP PCI DEVICE MEMORY
         Map the PCI device memory and get the virtual address and
size of the address.

          /* code snippet */
          fRegisterMap = fPCIDevice->mapDeviceMemoryWithRegister(uladdr);
          deviceRegisters  = (ati_reg *)fRegisterMap->getVirtualAddress();
         /********************/

Step 2)  MAP MEMORY TO USER LEVEL APPLICATION
          To map i plan to use clientMemoryForType()  in my kext

           /* code snippet */
          fMemoryToShare->retain();
          *memory = fMemoryToShare;
          /*********************/

Step 3) USER LEVEL APPLICATION PROCESS
         The user level application will open the driver and
communicate with the driver and      get the mapped memory region. See
the memory region using Xcode debugger, it will print the address and
memory location

             /* code snippet */
            IOConnectMapMemory() // to get the  mapped memory at use level
             /*****************/

Step 4) I2C COMMUNICATION THROUGH COMMANDS
          In the application use i2c api;s to read EDID data. This
will write/read parameters from the graphics card for i2c
communication with monitor  by writting/reading at some registers on
the graphics card.

/*code for EDID can be taken from*/
http://darwinsource.opendarwin.org/Current/IOGraphics-179.2/tools/i2cexample.c

Step 4) Check the memory changes
The address whose memory location changes will be the offset of the
i2c for data/clock

///////////////////////////////

Can you please comment if this approcah feasible and correct way to
find offset in a video graphics card of a particular register ?

Or there is any alternate methods for the same ? Any ideas?

The main objective is to find the offset and masking values of i2c
registers in a video graphics card, all suggestions are most welcome.

Please comment

Thanks and Regards,
Rohit

--
Rohit Dhamija(M) 9818446545
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