Query about PCI base address registers

[Ulka Vaze]

Hi,

   In PCI configuration space there are 6 registers BAR0-5 which can
hold the ioaddress or memory address used by card.
However my question is - how will we know which BAR register contain
ioaddress  and which contain memory ? and How many of them contain the
addresses. I mean shall we start reading from bar0 to 5 all to find it
?
If card  has 3 ports and one memory region  will it be in bar0 or bar1 or bar2 ?

Second is on PCI card we set it as bus master for DMA  in probe
function and also allocates buffer. So when is DMA  actually initiated
by it ?

Please can anybody clarify.

Thanks,
-Ulka




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