I think it might be that bio sets up the iov incorrectly.

I've had this problem that sdparm is receiving all-zero data (command
completes OK but no data is written into specified buffer) with kernel
2.6.19, and I've found that blk_rq_map_user receives the correct user
space buffer address but the iov generated for data transfer is not a
map to that user address.  So the low-level driver reads the data into
a wrong buffer. I'm running 2.6.19 on a dual-opteron box with 4G
memories, kernel compiled for x86_64. I haven't tried the git tree but
I've read all commit log ( til Dec 22nd ) and didn't find any commit
on this problem.

I thought it might be introduced in recent kernels ( 2.6.17-2.6.19 )
because sdparm works fine with SuSE Linux 10.1's kernel ( customized
2.6.16 ), which it seems is not the fact.

I planed to look into it further but is currently having no spare
time. If you've got an update, please let me know about it. TIA.

Cheers,
Albert Ke

On 12/22/06, Ken Hwang <[EMAIL PROTECTED]> wrote:
Hi,

I had a utility which uses SG_IO ioctl (scsi passthrough?) to issue private
commands to a USB dongle (reported as a USB Mass Storage but with 0 bytes)
to get some information back. It works fine with kernel 2.6.12.2. But after
we upgraded to kernel 2.6.15.4 then the program could not get information
back anymore (reads all 0 with the private command). Can anyone please give
me a hint of where I should go studying more?

Thanks,

Ken
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