Re: How do I access nvRAM from user space?

[David Hawkins]

Hi Bruce,

Thanks for the reply. So if my nvSRAM device is located at 0xb0000000 in physical memory, what would the mmap() call look like? Also, do I need to have a device tree entry for the kernel to know about the memory? I can access the device in uboot so I know it works, but I can't figure out the mmap to get it from linux

Its pretty much:

        /* Open /dev/mem and map it */
        printf(" * open /dev/mem\n");
        fd = open("/dev/mem", O_RDWR | O_SYNC);
        if (fd < 0) {
                printf("Open /dev/mem failed - %s\n",
                        strerror(errno));
                return -1;
        }
        printf(" * map %d page(s) (%d-bytes) at address 0x%.8X\n",
                        mem_pages, mem_size, mem_phys);
        mem_addr = (char *)mmap(
                0,
                mem_size,
                PROT_READ|PROT_WRITE,
                MAP_SHARED,
                fd,
                mem_phys);
        if (mem_addr == (char *)MAP_FAILED) {
                printf("Error: mmap failed\n");
                close(fd);
                return -1;
        }

I'll send you the code I ripped that from, and another
example from the Busybox code.

Cheers,
Dave



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