fix radeon setparam on 32/64 systems, harder.

Commit 9b01bd5 introduced a
compat_ioctl handler for RADEON_SETPARAM, the sole purpose of which was
to handle the fact that on i386, alignof(uint64_t)==4.

Unfortunately, this handler was installed for _all_ 64-bit
architectures, instead of only x86_64 and ia64.  And thus it breaks
32-bit compatibility on every other arch, where 64-bit integers are
aligned to 8 bytes in 32-bit mode just the same as in 64-bit mode.

Arnd has a cunning plan to use 'compat_u64' with appropriate alignment
attributes according to the 32-bit ABI, but for now let's just make the
compat_radeon_cp_setparam routine entirely disappear on 64-bit machines
whose 32-bit compat support isn't for i386.  It would be a no-op with
compat_u64 anyway.

Signed-off-by: David Woodhouse <dwmw2@infradead.org>
Acked-by: Arnd Bergmann <arnd@arndb.de>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: Dave Airlie <airlied@gmail.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

drivers/char/drm/radeon_ioc32.c

@@ -349,6 +349,8 @@ static int compat_radeon_irq_emit(struct file *file, unsigned int cmd,
 			 DRM_IOCTL_RADEON_IRQ_EMIT, (unsigned long)request);
 }
 
+/* The two 64-bit arches where alignof(u64)==4 in 32-bit code */
+#if defined (CONFIG_X86_64) || defined(CONFIG_IA64)
 typedef struct drm_radeon_setparam32 {
 	int param;
 	u64 value;
@@ -373,6 +375,9 @@ static int compat_radeon_cp_setparam(struct file *file, unsigned int cmd,
 	return drm_ioctl(file->f_dentry->d_inode, file,
 			 DRM_IOCTL_RADEON_SETPARAM, (unsigned long) request);
 }
+#else
+#define compat_radeon_cp_setparam NULL
+#endif /* X86_64 || IA64 */
 
 drm_ioctl_compat_t *radeon_compat_ioctls[] = {
 	[DRM_RADEON_CP_INIT] = compat_radeon_cp_init,