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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