[sane-devel] Slightly off topic: Anyone know anything about SCSI CD commands?

Tue Jan 6 18:37:04 UTC 2009

On Tue, 6 Jan 2009, Gerard Klaver wrote:

> On Mon, 2009-01-05 at 17:24 -0600, kilgota at banach.math.auburn.edu wrote:
>> Wishing everyone a prosperous, happy, and peaceful year 2009.
>>
>> For a lark, I bought a rather worthless but very cheap gadget for myself
>> for Christmas. It is a very small digital picture frame which one can hang
>> on the key ring. The little book which came with it says that to use it,
>> one merely plugs it in on a computer running XP or Vista, and the app is
>> already installed which will communicate with it. I tried this, and it is
>> so. With the app, one can view JPEG images on the device, also move images
>> to/from, and delete what is on the device. Then, the device has a
>> primitive OS which will allow various things to be done, such as to
>> display the time instead of a picture. It also gets reported as an
>> external drive, with the information that it is "full" and AFAIK one
>> cannot access it directly.
>>
>> I made one snoop log, which probably does not yet have the serious
>> information needed to continue with this thing. I spent most of my time
>> fighting Vista to get the log made.
>>
>> So much for the background. What it is, is a Mass Storage Bulk Transport
>> device which comes up as a /dev/sg, not as a /dev/sd. So in other words it
>> is possible to talk to it with Mass Storage Bulk Transport, but one can
>> not mount it. In other words, similar to some audio CDs, or to some
>> scanners. In the forwarded message below, there is some report of the
>> results of various commands, and also a question at the end, about a
>> certain SCSI command with which I am not acquainted and can not seem to
>> find relevant documentation. I hope that someone can help me with the
>> question.
>>
>> Theodore Kilgore
>>
>>
>> ---------- Forwarded message ----------
>> Date: Mon, 5 Jan 2009 12:57:13 -0600 (CST)
>> From: kilgota at banach.math.auburn.edu
>> To: Pete Zaitcev <zaitcev at redhat.com>
>> Cc: usb-storage at lists.one-eyed-alien.net
>> Subject: Re: [usb-storage] A keychain digital picture frame.
>>
>>
>>
>> On Thu, 1 Jan 2009, Pete Zaitcev wrote:
>>
>>> On Thu, 1 Jan 2009 21:34:00 -0600 (CST), kilgota at banach.math.auburn.edu
>>> wrote:
>>>
>>>> I successfully made a snoop log of one photo being moved over to the
>>>> device. Indeed, it appears to be using Mass Storage Bulk Transport
>>>> commands.
>>>
>>> Try to eject the pseudo-CD on Linux, maybe the device will re-enumerate
>>> itself then.
>>>
>>> -- Pete
>>>
>>
>> Well, as I mentioned earlier, the eject did not work. Therefore, I have done a
>> bit of looking through that log file. I have also gotten a copy of sg3-utils
>> and played with it a little bit.
>>
>> One thing seems clear, that the device reports itself as a CD. The sectors are
>> 2048 bytes, and it uses READ_10 to read a sector, or sectors. Lots of fairly
>> routine stuff. Some selections:
>>
>>      00000000: 55 53 42 43 c8 e6 95 84 08 00 00 00 80 00 0a 25
>>      00000010: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
>>
>> reports
>>
>>      00000000: 00 01 e7 ff 00 00 08 00 (0x1e7ff sectors of size 0x800)
>>
>> so I wonder if it has the off-by-one error. It would not make any difference
>> unless one were going to mount it, I suppose...
>>
>> I do not know enough about this to understand the response to REQUEST_SENSE
>>
>>      00000000: 55 53 42 43 88 d5 9f 84 12 00 00 00 80 00 0c 03
>>      00000010: 00 00 00 12 00 00 00 00 00 00 00 00 00 00 00
>>
>> which gets various responses. One of them is
>>
>>      00000000: f0 00 02 00 00 00 00 0b 00 00 00 00 3a 00 00 00
>>      00000010: 00 53
>>
>> Windows keeps insisting on sending
>>
>>      00000000: 55 53 42 43 28 3e 6e 84 20 00 00 00 80 00 0a 51
>>      00000010: 00 00 00 00 00 00 00 20 00 00 00 00 00 00 00
>>
>> which makes the device to throw a fit, and a reset is required. I think that
>> this has something to do with initializing RAID setup?
>>
>> Now, scsi.h says the following one is READ_TOC:
>>
>>      00000000: 55 53 42 43 88 2b 82 84 0c 00 00 00 80 00 0a 43
>>      00000010: 00 01 00 00 00 00 00 0c 00 00 00 00 00 00 00
>>
>> I do not understand what the response might be telling me, which is
>>
>>      00000000: 00 0a 01 01 01 14 00 a0 00 00 00 00
>>
>> though I do vaguely remember that the device claimed to have room for 45
>> images. The numbers strung out here do add up to that, which might or might not
>> be significant.
>>
>>
>> Here is a sample of READ_10
>>
>>      00000000: 55 53 42 43 c8 e6 95 84 00 08 00 00 80 00 0a 28
>>      00000010: 00 00 00 00 19 00 00 01 00 00 00 00 00 00 00
>>
>> (read one sector at 0x19)
>> to which the reply begins with
>>
>>      00000000: 5b 41 55 54 4f 52 55 4e 5d 0d 0a 49 43 4f 4e 3d
>>                 A  u  t  o  r  u  n     i  c  o        O  P  E
>>      00000010: 41 75 74 6f 72 75 6e 2e 69 63 6f 0d 0a 4f 50 45
>>      00000020: 4e 3d 49 6d 61 67 65 56 69 65 77 65 72 34 2e 65
>>                 x  e     -  C  O  P  Y  F  I  L  E
>>      00000030: 78 65 20 2d 43 4f 50 59 46 49 4c 45 00 00 00 00
>>      00000040: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
>>      00000050: 00 00 00 (the rest of the sector is empty)
>>
>> and then
>>
>>      00000000: 55 53 42 43 08 00 5b 84 38 00 00 00 80 00 0c 12
>>      00000010: 00 00 00 38 00 00 00 00 00 00 00 00 00 00 00
>>
>> followed by a "reply" (my annotations, which could be partly wrong of course)
>>
>> 05 means CDROM 0x80 means removable medium then 0s means scsi(?) and 02(?)
>> 1f is something about extra length and then
>>
>>                                         I  n  s  i  g  n  i  a
>>      00000000: 05 80 02 02 1f 00 00 00 49 6e 73 69 67 6e 69 61
>>                 N  S  -  D  K  U  Y  X  X  0  9
>>      00000010: 4e 53 2d 44 4b 45 59 58 58 30 39 00 20 20 20 20
>>                             t  e  n  x  d  s  k        E  Y  X
>>      00000020: 00 20 20 20 74 65 6e 78 64 73 6b 00 00 45 59 58
>>                 X  0  9
>>      00000030: 58 30 39 00 20 20 20 20
>>
>>
>> But then I got a bit of the way through the log file, and it came up with
>>
>>      00000000: 55 53 42 43 08 00 5b 84 00 80 00 00 80 00 0c c1
>>      00000010: 11 31 0f 30 01 80 00 00 00 00 00 00 00 00 00
>>
>> to which the reply is a block, and then the command is repeated, apparently
>> with a different answer, then still a third time (at least).
>>
>> I cannot find much information about the SCSI command 0xc1. What little I did
>> find would lead me to believe that, again, it has something to do with a CD.
>> Does anyone know where to learn more about this, or actually know the
>> information, to save the trouble of chasing it?
>>
>>
>> Theodore Kilgore
>>
>
> Seems like same sort of device i have, see
> http://gkall.hobby.nl/dpf018.html for some information.
>
>
> -- 
> --------
> m.vr.gr.
> Gerard Klaver
>

Interesting. I provided sundry information about the little creature in a 
previous post to usb-storage which you can find in Usb-storage Digest, Vol 
59, Issue 2. I will also forward that e-mail here. It has the output of 
/proc/bus/usb/devices and dmesg output, that kind of good stuff. Perhaps 
we can compare notes. However, I have the impression that there are 
significant differences between these devices, in spite of the similarity 
of function.

As I said, I will forward the other e-mail here, and to you.

Theodore Kilgore