Messages in this thread | | | Date | Thu, 30 Aug 2012 21:00:19 +0200 | From | "Hans J. Koch" <> | Subject | Re: Using uio_pdrv to create an platform device for an FPGA, mmap() fails |
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On Thu, Aug 30, 2012 at 06:36:53PM +0000, Worth, Kevin wrote: > 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.
Good.
> > 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.
You're right. That wants to be fixed...
> > 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.
If you want to have that included in the mainline, please choose a more descriptive name than "myfpga" and send a proper patch.
Thanks, Hans
> > -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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