Hi,
I have just modified a program which was accessing a tar file (look
in linux-userfs for more questions :)), using fread() and also
fseek().
I wanted to modify the software to also accept /dev/st0 as file,
as long as all fseek()s are done forward.
It did not work, so in the end I have rolled-my-own fseek() implemented
as dummy fread()s. This is satisfactory at this time, but I would
like to understand more. It also supports going backwards, at this
time by closing/reopening the rewinding tape device, and then reading
from 0. I am pleased since this works perfectly.
My question:
- How is fseek() be implemented when the seeks are forward only
with a tape drive (st.c) ? (really: how is read() implemented
when the file offset has augmented)
- And when the seeks are all directions ?
I am interested by the current implementation. In theory DAT drives
can be exactly (on a record basis) positionned in all directions. Other
drives might only support going forward or backward a certain number of
blocks. But in any case, the driver could emulate what I have hacked
in my user-land software. Or, if it doesn't support it, it could
return an error. It *looked* that the seek comportment was not
right, and that no error was returned.
If noone answers, I will try to understand by myself, however, at this
time it's probably better if someone already knowing can help me.
Please Cc: me since I am not sure I receive linux-scsi completely.
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