Messages in this thread | | | From | "Worth, Kevin" <> | Subject | RE: Using uio_pdrv to create an platform device for an FPGA, mmap() fails | Date | Thu, 30 Aug 2012 18:36:53 +0000 |
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Thanks for the reply, Hans. Your question about opening /dev/uio0 O_RDWR prompted me to check out how I was creating /dev/uio0 ... my system isn't using udev, and I was accidentally creating it with major/minor number 254/0 instead of the correct 253/0 (found by looking at /proc/devices). Fixed that and the mmap() call started working.
Verified that if /dev/uio0 has permissions 0644, root can open it O_RDWR and mmap PROT_READ | PROT_WRITE using the below code and write to an address within my memory map. Of course this contradicts the statement "/dev/uioX is a read-only file" in the UIO howto.
Including my updated, tested code for completeness. Note I also cleaned up the device registration a little by using a different platform_device_register_ call and removing fields in the struct uio_info that get filled in by uio_pdrv automatically.
-Kevin
# lsuio -m -v uio0: name=uio_myfpga, version=0.1, events=0 map[0]: addr=0xD0000000, size=262144, mmap test: OK Device attributes: uevent=DRIVER=uio_pdrv modalias=platform:uio_pdrv
------Kernelspace------ #include <linux/platform_device.h> #include <linux/uio_driver.h> #include <linux/module.h>
#define MYFPGA_BASE 0xd0000000 // 3G #define MYFPGA_SIZE 0x00040000 // 256k
static struct resource myfpga_resources[] = { { .start = MYFPGA_BASE, .end = MYFPGA_BASE + MYFPGA_SIZE - 1, .name = "myfpga", .flags = IORESOURCE_MEM } };
static struct uio_info myfpga_uio_info = { .name = "uio_myfpga", .version = "0.1", };
static struct platform_device *myfpga_uio_pdev;
static int __init myfpga_init(void) { myfpga_uio_pdev = platform_device_register_resndata (NULL, "uio_pdrv", -1, myfpga_resources, 1, &myfpga_uio_info, sizeof(struct uio_info) ); if (IS_ERR(myfpga_uio_pdev)) { return PTR_ERR(myfpga_uio_pdev); }
return 0; }
static void __exit myfpga_exit(void) { platform_device_unregister(myfpga_uio_pdev); }
module_init(myfpga_init); module_exit(myfpga_exit);
------Userspace------- #include <sys/types.h> #include <sys/mman.h> #include <sys/stat.h>
#include <dirent.h> #include <string.h> #include <stdlib.h> #include <stdio.h> #include <fcntl.h> #include <unistd.h> #include <stdint.h>
#define MYFPGA_BASE 0xd0000000 // 3G #define MYFPGA_SIZE 0x00040000 // 256k #define MYFPGA_MAP_NUM 0 // First and only defined map
#define BIT32(n) (1 << (n))
/* Use mmap()'ped address "iomem", not physical MYFPGA address */ #define MYFPGA_REG(iomem) (volatile uint32_t*)(iomem + 0x8) // Third 32-bit reg
int main (int argc, char *argv[]) { int fd; void *iomem; fd = open("/dev/uio0", O_RDWR|O_SYNC); if (fd < 0) { printf("failed to open /dev/uio0, quitting\n"); return -1; } /* Note offset has a special meaning with uio devices */ iomem = mmap(NULL, MYFPGA_SIZE, PROT_READ | PROT_WRITE, MAP_SHARED, fd, MYFPGA_MAP_NUM * getpagesize()); if (iomem == MAP_FAILED) { printf("mmap failed, quitting\n"); close(fd); return -2; }
/* Set bit 5 of MYFPGA_REG register */ *MYFPGA_REG(iomem) |= BIT32(5);
munmap(iomem, MYFPGA_SIZE); close(fd); return 0; }
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