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 20:10:11 +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. > >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.
I wasn't sure about submitting as a patch since it's for a custom FPGA that I don't expect the community will be using, but the code seems like possibly useful sample/example code. Perhaps patching the HOWTO like http://www.kernel.org/doc/htmldocs/uio-howto.html#uio_pci_generic_example is the right approach?
> >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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