Messages in this thread | | | Date | Fri, 31 Aug 2012 00:24:08 +0200 | From | "Hans J. Koch" <> | Subject | Re: Using uio_pdrv to create an platform device for an FPGA, mmap() fails |
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[Added Greg Kroah-Hartman to Cc:]
On Thu, Aug 30, 2012 at 08:10:11PM +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. > > 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,
That doesn't matter. If it helps YOU that the code is maintained in mainline, post it.
> but the code seems like > possibly useful sample/example code.
That is another good argument.
> Perhaps patching the HOWTO like > http://www.kernel.org/doc/htmldocs/uio-howto.html#uio_pci_generic_example > is the right approach?
Oh, if you could hack up a patch for the documentation, that would be great. But please make it a second patch, don't mix it with your driver code.
Thanks, Hans
> > > > >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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