I add these lines in my kernel config file: device mmcsd device mmc then I got: cc -c -O2 -pipe -fno-strict-aliasing -Wall -Wredundant-decls -Wnested-externs -Wstrict-prototypes -Wmissing-prototypes -Wpointer-arith -Winline -Wcast-qual -fformat-extensions -std=c99 -nostdinc -I- -I. -I../../.. -I../../../contrib/altq -I../../../contrib/ipfilter -I../../../contrib/pf -I../../../dev/ath -I../../../contrib/ngatm -I../../../dev/twa -D_KERNEL -DHAVE_KERNEL_OPTION_HEADERS -include opt_global.h -fno-common -finline-limit=8000 --param inline-unit-growth=100 --param large-function-growth=1000 -mno-align-long-strings -mpreferred-stack-boundary=2 -mno-mmx -mno-3dnow -mno-sse -mno-sse2 -ffreestanding -Werror ../../../dev/mmc/mmc.c awk -f ../../../tools/makeobjops.awk ../../../dev/mmc/mmcbr_if.m -c awk -f ../../../tools/makeobjops.awk ../../../dev/mmc/mmcbr_if.m -c ; cc -c -O2 -pipe -fno-strict-aliasing -Wall -Wredundant-decls -Wnested-externs -Wstrict-prototypes -Wmissing-prototypes -Wpointer-arith -Winline -Wcast-qual -fformat-extensions -std=c99 -nostdinc -I- -I. -I../../.. -I../../../contrib/altq -I../../../contrib/ipfilter -I../../../contrib/pf -I../../../dev/ath -I../../../contrib/ngatm -I../../../dev/twa -D_KERNEL -DHAVE_KERNEL_OPTION_HEADERS -include opt_global.h -fno-common -finline-limit=8000 --param inline-unit-growth=100 --param large-function-growth=1000 -mno-align-long-strings -mpreferred-stack-boundary=2 -mno-mmx -mno-3dnow -mno-sse -mno-sse2 -ffreestanding -Werror mmcbr_if.c In file included from mmcbr_if.c:20: ./mmcbr_if.h:20: error: syntax error before "brdev" ./mmcbr_if.h:20: warning: function declaration isn't a prototype ./mmcbr_if.h:22: error: syntax error before "brdev" ./mmcbr_if.h:23: warning: function declaration isn't a prototype ./mmcbr_if.h: In function `MMCBR_UPDATE_IOS': ./mmcbr_if.h:25: error: `brdev' undeclared (first use in this function) ./mmcbr_if.h:25: error: (Each undeclared identifier is reported only once ./mmcbr_if.h:25: error: for each function it appears in.) ./mmcbr_if.h:26: error: `reqdev' undeclared (first use in this function) ./mmcbr_if.h: At top level: ./mmcbr_if.h:32: error: syntax error before "brdev" ./mmcbr_if.h:33: warning: function declaration isn't a prototype ./mmcbr_if.h:35: error: syntax error before "brdev" ./mmcbr_if.h:37: warning: function declaration isn't a prototype ./mmcbr_if.h: In function `MMCBR_REQUEST': ./mmcbr_if.h:39: error: `brdev' undeclared (first use in this function) ./mmcbr_if.h:40: error: `reqdev' undeclared (first use in this function) ./mmcbr_if.h:40: error: `req' undeclared (first use in this function) ./mmcbr_if.h: At top level: ./mmcbr_if.h:46: error: syntax error before "brdev" ./mmcbr_if.h:46: warning: function declaration isn't a prototype ./mmcbr_if.h:48: error: syntax error before "brdev" ./mmcbr_if.h:49: warning: function declaration isn't a prototype ./mmcbr_if.h: In function `MMCBR_GET_RO': ./mmcbr_if.h:51: error: `brdev' undeclared (first use in this function) ./mmcbr_if.h:52: error: `reqdev' undeclared (first use in this function) ./mmcbr_if.h: At top level: ./mmcbr_if.h:58: error: syntax error before "brdev" ./mmcbr_if.h:58: warning: function declaration isn't a prototype ./mmcbr_if.h:60: error: syntax error before "brdev" ./mmcbr_if.h:61: warning: function declaration isn't a prototype ./mmcbr_if.h: In function `MMCBR_ACQUIRE_HOST': ./mmcbr_if.h:63: error: `brdev' undeclared (first use in this function) ./mmcbr_if.h:64: error: `reqdev' undeclared (first use in this function) ./mmcbr_if.h: At top level: ./mmcbr_if.h:70: error: syntax error before "brdev" ./mmcbr_if.h:70: warning: function declaration isn't a prototype ./mmcbr_if.h:72: error: syntax error before "brdev" ./mmcbr_if.h:73: warning: function declaration isn't a prototype ./mmcbr_if.h: In function `MMCBR_RELEASE_HOST': ./mmcbr_if.h:75: error: `brdev' undeclared (first use in this function) ./mmcbr_if.h:76: error: `reqdev' undeclared (first use in this function) *** Error code 1 -- Oops