Created attachment 32919 [details]
Xorg.log

on a gentoo "amd64" system, i have the following version installed :

xorg-x11-7.4-r1
xorg-server-1.6.5-r1
xf86-input-evdev-2.3.1

when i press a multimedia key ( XF86Mail / XF86AudioPlay / etc. ) of my Dell USB Keyboard ( 413c:2010 ) , Xorg SIGSEGV with following backtrace :

Backtrace:
0: /usr/bin/X(xorg_backtrace+0x26) [0x4ec5d6]
1: /usr/bin/X(xf86SigHandler+0x39) [0x497679]
2: /lib/libc.so.6 [0x7ff64a9c13a0]           
3: /usr/bin/X [0x45dca0]                     
4: /usr/bin/X(GetKeyboardValuatorEvents+0x362) [0x45e242]
5: /usr/bin/X(GetKeyboardEvents+0x17) [0x45e327]         
6: /usr/bin/X(xf86PostKeyboardEvent+0x6f) [0x474e5f]     
7: /usr/lib64/xorg/modules/input//evdev_drv.so [0x7ff63734a9bf]
8: /usr/bin/X [0x497765]                                       
9: /usr/bin/X [0x4707d9]                                       
10: /lib/libpthread.so.0 [0x7ff64ca72df0]                      
11: /lib/libc.so.6(__select+0x13) [0x7ff64aa58dd3]             
12: /usr/bin/X(WaitForSomething+0x1cb) [0x4ea19b]              
13: /usr/bin/X(Dispatch+0xa0) [0x44b3b0]                       
14: /usr/bin/X(main+0x3aa) [0x43155a]                          
15: /lib/libc.so.6(__libc_start_main+0xe6) [0x7ff64a9ada26]    
16: /usr/bin/X [0x4309f9]                                      

Fatal server error:
Caught signal 11.  Server aborting

i have spied on the strace output of the crash but it does not help me :
...
read(27, 0x110b080, 4096)               = -1 EAGAIN (Resource temporarily unavailable)
writev(27, [{"\1\1\213\342\0\0\0\0\31\0\340\2\0\0\0\0\300h\213\1\0\0\0\0\0\0\0\0\0\0\0\0", 32}], 1) = 32
setitimer(ITIMER_REAL, {it_interval={0, 0}, it_value={0, 0}}, NULL) = 0
select(256, [1 3 5 7 9 10 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 46], NULL, NULL, {0, 67000}) = 13 (in [10 20 22 24 27 29 33 34 35 36 37 38 46], left {0, 66995})
setitimer(ITIMER_REAL, {it_interval={0, 20000}, it_value={0, 20000}}, NULL) = 0
read(27, "!\1\4\0\34\1\0\0@\0\n\1\0{\3\0!\1\4\0\34\1\0\0B\0\n\1\0\1\0\0"..., 4096) = 132
read(27, 0x110b080, 4096)               = -1 EAGAIN (Resource temporarily unavailable)
--- SIGIO (I/O possible) @ 0 (0) ---
select(46, [8 11 12 13 14 15 16 45], NULL, NULL, {0, 0}) = 1 (in [11], left {0, 0})
rt_sigprocmask(SIG_BLOCK, [IO], [IO], 8) = 0
read(11, "[\n^K\0\0\0\0<N\7\0\0\0\0\0\1\0r\0\1\0\0\0[\n^K\0\0\0\0"..., 384) = 96
--- SIGSEGV (Segmentation fault) @ 0 (0) ---
rt_sigaction(SIGSEGV, {SIG_IGN, [SEGV], SA_RESTORER|SA_RESTART, 0x7fc74b6273a0}, {0x497640, [SEGV], SA_RESTORER|SA_RESTART, 0x7fc74b6273a0}, 8) = 0
write(2, "\nBacktrace:\n", 12)          = 12
write(0, "\nBacktrace:\n", 12)          = 12
...
let me know if more could help.

i have tried lots of things with evdev fdi files and xorg.conf, but i have found no solution on the ".conf" side.
i believe the issue could be 64bit related because it also occurs with a livecd of sabayon for x86_64 (Sabayon_Linux_5.1-r1_amd64_K.iso) whereas it does not occur with the x86 edition (Sabayon_Linux_5.1-r1_x86_K.iso)
i'm able to recompile anything as long as it is the same versions as the current gentoo ebuilds, i'd be glad to help by testing a patch or provide more specific traces if needed.