<div dir="ltr"><div class="gmail_extra">Please see my question inline.</div><div class="gmail_extra"><br></div><div class="gmail_extra">Thanks in Advance,</div><div class="gmail_extra">Dhananjay<br><br><div class="gmail_quote">
On Mon, Apr 1, 2013 at 9:42 AM, Avinash Patil <span dir="ltr"><<a href="mailto:avinashapatil@gmail.com" target="_blank">avinashapatil@gmail.com</a>></span> wrote:<br><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">
<div dir="ltr">AFAIK.<div class="im"><br><br><div>1) as we know pci_alloc_consistent allocates dma buffers which is visible to DMA controller as well as CPU.</div>
<div> virt_add = pci_alloc_consistent(pdev, size, dma_addr_t bus_adrr);</div><div><br></div><div>here it will allocate a buffer and return its virtual address and corresponding bus address.</div><div>
<br></div><div>My question is do these two address ultimately point to similar location but from different perspectives ?.<br><br></div></div><div>Avinash: Yes both virtual and physical addresses point to same location. BAR at the enumeration of PCI devices allocates specific address for PCI devices from RAM and your alloc_consistent uses these addresses.<br>
</div><div class="im"><div><br></div></div></div></blockquote><div style>Dhananjay : I am quiet confused about what do you mean by "these" addresses here ?. Do you mean dma buffer bus address allocated by alloc_consistent or BAR bus addresses which can be seen in /proc/pci ?</div>
<div> </div><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex"><div dir="ltr"><div class="im"><div></div><div>2) After allocating these address, how do we proceed given that i have a ASIC register which has the dma_rx_desc_start address ?</div>
</div><div>Avinash: Here is a link which can help you for creating rings, creating your ISR which handles different vendor specific interrupts etc<br><br><a href="http://netsecinfo.blogspot.in/search?q=PCIe" target="_blank">http://netsecinfo.blogspot.in/search?q=PCIe</a><br>
<br></div><div>Avinash: <br></div><div class="im"><div>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 ?<br></div></div><div>Avinash: These structures are vendor specific which may contain physical address, length etc.<br></div>
<br></div><div class="gmail_extra"><br><br><div class="gmail_quote"><div class="im">On Thu, Mar 28, 2013 at 1:14 AM, Dhananjay Maske <span dir="ltr"><<a href="mailto:dhananjay.maske87@gmail.com" target="_blank">dhananjay.maske87@gmail.com</a>></span> wrote:<br>
</div><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex"><div><div class="h5"><div dir="ltr">Hi All,<div> I am fairly New to Linux kernel Programming and i have few questions with respect to pci_alloc_consistent .</div>
<div><br></div><div>1) as we know pci_alloc_consistent allocates dma buffers which is visible to DMA controller as well as CPU.</div>
<div> virt_add = pci_alloc_consistent(pdev, size, dma_addr_t bus_adrr);</div><div><br></div><div>here it will allocate a buffer and return its virtual address and corresponding bus address.</div><div>
<br></div><div>My question is do these two address ultimately point to similar location but from different perspectives ?.</div><div><br></div><div>2) After allocating these address, how do we proceed given that i have a ASIC register which has the dma_rx_desc_start address ?</div>
<div><br></div><div>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 ?</div>
</div>
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