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Is there any method of reading and writing more than 1 DW from the user-space of PCI device? I am currently using https://github.com/numato-viya/pcimem this code for accessing the data from the user space of the PCI device but the limitation of this code is it can access only 1 DW from the Userspace. But I want to access more than one DW from the userspace in one TLP. Can you help me how to access more than 1DW in one TLP?

Hamayoun Ahmad
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  • Do you mean you want to access a QWORD, or do you mean you want to access a bunch of consecutive DWORDs? If the latter, I think there's no way to do it from the CPU. (I'm sure there's no way to do it from an x86 or x86-64 CPU; I'm less sure about other types of processors. You didn't mention your CPU architecture.) – prl Jan 16 '18 at 07:57
  • Currently, I am using my Ubuntu OS on my Intel core I7 4th generation processor for accessing a bunch of consecutive DWORDs in one TLP from my memory implemented on my PCIe device. – Hamayoun Ahmad Jan 19 '18 at 04:59
  • Sorry for miss understanding currently I am not accessing a bunch of consecutive DWORDs I am trying to access. – Hamayoun Ahmad Jan 19 '18 at 09:20

2 Answers2

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You could easily add a 'd' option to that code to use a uint64_t. On a 64-bit processor, it would generate an 8-byte access. The device is not obligated to support 8-byte accesses, though.

prl
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  • Thanks for quick reply. I tried "uint64_t " but this doesn't work because I am using a 32-bit address line mode. Actually, I am trying to find a way to increase the length of TLP. – Hamayoun Ahmad Jan 19 '18 at 04:55
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You can use AVX instructions to perform larger memory transfers. AVX512 can move 64 bytes in a single operation.

prl
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