write(2) to /dev/ad4 = EINVAL

[Lukasz Jaroszewski]

Hi,
after opening /dev/ad4 with success for O_RDWR, I am getting [EINVAL]
from write(2), which according to man 2 write, means
 ``     [EINVAL]           The pointer associated with d was
negative.'', as you can see below it is not true, I have tried
different block sizes, with same result.

How can I write one byte to /dev/adN ?


1361 ow       CALL  open(0x80485e3,O_RDWR,<unused>0xbfbfecc8)
1361 ow       NAMI  "/dev/ad4"
                       ;/dev/ad4 is DOS FAT formatted CF Card.
1361 ow       RET   open 3

1361 ow       CALL  write(0x3,0xbfbfecb8,0x8)
1361 ow       RET   write -1 errno 22 Invalid argument

root@~(0) uname -r
7.0-STABLE
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Best Regards
Lukasz.