Hello PCI endpoint maintainers, While looking at the pci-epf-test.c driver, I noticed that pci-epf-test is completely broken with regards to endianness. As you probably know, PCI devices are inherently little-endian, and the data stored in the PCI BARs should be in little-endian. However, pci-epf-test does no conversion before storing the data to backing memory, and no conversion after reading the data from backing memory. For the data backing test_reg BAR (usually BAR0), which has the format as defined by struct pci_epf_test_reg, is simply stored to memory using e.g.: reg->status = STATUS_WRITE_SUCCESS; Surely, this should be: reg->status = cpu_to_le32(STATUS_WRITE_SUCCESS); Likewise the src and dst address is accessed simply by reg->dst_addr and reg->src_addr. Surely, this should be accessed using: dst_addr = le64_to_cpu(reg->dst_addr); src_addr = le64_to_cpu(reg->src_addr); So bottom line, pci-epf-test will currently not behave correctly on big-endian. Looking at pci-endpoint-test however, it does all its accesses using readl() and writel(), and if you look at the implementations of readl()/writel(): https://github.com/torvalds/linux/blob/v6.12-rc4/include/asm-generic/io.h#L181-L184 They convert to CPU native after reading, and convert to little-endian before writing, so pci-endpoint-test (RC side driver) is okay, it is just pci-epf-test (EP side driver) that is broken. I'm not planning on spending time on this, but I thought that I ought to at least report it, such that maintainers/developers/users are aware of it. Kind regards, Niklas
