On 07/24/13 22:09, Damjan Jovanovic wrote:

The ioctl:
#define USB_FS_INIT             _IOW ('U', 195, struct usb_fs_init)
when used by a COMPAT_32BIT libusb on amd64, fails (causing
libusb_open() to fail) due to:

freebsd32_ioctl(0x6,0x800c55c3,0xffffc710,0x0,0x0,0x0) ERR#25
'Inappropriate ioctl for device'
but when hacked a bit:
freebsd32_ioctl(0x6,0x801055c3,0xffffc710,0x0,0x0,0x0) = 0 (0x0)

because sizeof(struct usb_fs_init) is 12 bytes on i386, and 16 bytes on amd64.

But the failure of even libusb_open() - a fundamental libusb function
- must mean that the COMPAT_32BIT libusb never worked. Can we please
take this opportunity to kill it and do a real 32 bit compatibility
layer in the kernel that will work from 32 bit chroots and statically
linked 32 bit binaries? I'll help.


Some further analysis shows that this is due to structures being aligned to their biggest element on AMD64 while on I386 not. This should now be fixed. Please see the following commit:


You will need to use the LibUSB-32 built by the 64-bit system build, and not the I386 one, which has COMPAT_32BIT set.

Thank you!


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