pci_alloc_consistent doubt

[Dhananjay Maske]

Hi All,
     I am fairly New to Linux kernel Programming and i have few questions
with respect to pci_alloc_consistent .

1) as we know pci_alloc_consistent allocates dma buffers which is visible
to DMA controller as well as CPU.
    virt_add = pci_alloc_consistent(pdev, size, dma_addr_t bus_adrr);

here it will allocate a buffer and return its virtual address and
corresponding bus address.

My question is do these two address ultimately point to similar location
but from different perspectives ?.

2) After allocating these address, how do we proceed given that i have a
ASIC register which has the dma_rx_desc_start address ?

3) Also does all the HW's which support dma have the descriptor data
structures by provided by Vender or is there any specific format that dev
has to be aware of for designing such descriptor for that particular driver
?
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