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Message-ID: <20120830222408.GC4819@local>
Date: Fri, 31 Aug 2012 00:24:08 +0200
From: "Hans J. Koch" <hjk@...sjkoch.de>
To: "Worth, Kevin" <kevin.worth@...com>
Cc: "Hans J. Koch" <hjk@...sjkoch.de>,
"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
"u.kleine-koenig@...gutronix.de" <u.kleine-koenig@...gutronix.de>,
Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Subject: Re: Using uio_pdrv to create an platform device for an FPGA, mmap()
fails
[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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