Determing Display PCI Device ID

[James Milne]

Is there an API for programmatically determining the PCI Vendor and 
Device ID of a given X display?

I want to use these IDs to search through a table of known good GL 
functionality (for example, floating point texture filtering), where the 
availablility of the functionality is not otherwise exposed through the 
GL extensions string.

I'm not interested in processing the output of scanpci or lspci. I'd 
also like this code to work in the situation where there are multiple 
graphics card in a system, so I'd like to map each X Display to a 
specific PCI device/vendor ID.

Any suggestions?

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Kind regards,
James Milne