A question on endpoint_test code in the linux source by Kishon Vijay Abraham I.

Chan Kim ckim at etri.re.kr
Thu Sep 14 01:38:49 EDT 2023

Hello linux experts,

I was analyzing drivers/misc/pci_endpoint_test.c (linux-5.15.68)
It uses a miscdev and when the driver receives PCITEST_WRITE command using
ioctl(line 726 in the link below) from the user, the driver sets registers
of the endpoint device and writes COMMAND_READ at register
test.c#L553 ). This seems to be setting DMA paramaters (source DMA address
and size) and triggering DMA. The driver then waits for completion and I can
see the interrupt service routine completes the
completion(test->irq_raised). I guess the endpoint device should actually do
the DMA-read (when told to use DMA) or read the data to itself(I don't know
where it is) and send interrupt to the host(using msix or msi or intx).

The code was written by "Kishon Vijay Abraham I" and I know it is supposed
to be run with drivers/pci/endpoint/functions/pci-epf-test.c
ions/pci-epf-test.c)  in the endpoint side. And how to use this endpoint
framework test is shown in
https://docs.kernel.org/PCI/endpoint/pci-test-howto.html . But I cannot find
where the actual DMA and sending interrupt is occurring in the endpoint side
source code when the registers at set. Am I supposed to be running this code
with some real hardware?(as listed in the pci_device_id in the hostside
pci_endpoint_test.c driver?) Where can I find the corresponding (acting on
the register triggering above) action in the endpoint side?

If you have once seen these codes and send me any hint or suggestion, I'll
be grateful.
Thank you.

Best regards,
Chan Kim

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