Re: [PATCH] st.c for GET_IDLUN 2.6.6-rc2

[Douglas Gilbert <dougg@torque.net>]

Kai Makisara wrote:
> On Mon, 26 Apr 2004, Douglas Gilbert wrote:
> 
> 
>>Kai Makisara wrote:
> 
> ....
> 
>>>2. Reversing the order of calls in st so that scsi_ioctl is called first 
>>>and if it returns -ENOTTY, then scsi_cmd_ioctl is called. This would 
>>>require changing scsi_ioctl to return -ENOTTY for commands not being 
>>>handled but would be othewise a logical solution: first try SCSI specific 
>>>implementation of the ioctl, if it does not exist, then try the block 
>>>layer version (Linux block layer, not Unix block layer ;-).
>>
>>This solution looks cleaner.
>>
> 
> I looked at the necessary changes a little more carefully and I think
> your solution is better from the practical point of view. The problem in  
> my solution is to make sure that scsi_ioctl() returns -ENOTTY in case it 
> does not implement the ioctl. This is easy except for the default case:
> 
>                 if (sdev->host->hostt->ioctl)
>                         return sdev->host->hostt->ioctl(sdev, cmd, arg);
> 
> where any kind of code can be found ;-) It is safer to leave this as the
> last resort.

Kai,
Here is another take on this matter. A summary of the ioctls
defined in block/scsi_ioctl.c follows with my comments:

ioctls defined in
block/scsi_ioctl.c          Comment
==================          =======
SCSI_IOCTL_SEND_COMMAND     redirects to scsi mid level
SCSI_IOCTL_GET_IDLUN        yields 0 (wrong, trips up cdrecord??)
SCSI_IOCTL_GET_BUS_NUMBER   yields 0 (wrong)
SG_EMULATED_HOST            irrelevant to st (obsolete in sg)
SG_GET_RESERVED_SIZE        irrelevant to st (to trick cdrecord)
SG_GET_TIMEOUT              irrelevant to st (to trick cdrecord)
SG_GET_VERSION_NUM          irrelevant to st (to trick cdrecord)
SG_IO                       <<< only ioctl useful to st (+ osst) >>
SG_SET_RESERVED_SIZE        irrelevant to st (to trick cdrecord)
SG_SET_TIMEOUT              irrelevant to st (to trick cdrecord)
CDROM_SEND_PACKET           irrelevant
CDROMCLOSETRAY              irrelevant
CDROMEJECT                  irrelevant

So if st just redirects only the SG_IO ioctl to scsi_cmd_ioctl()
and lets the rest go to the scsi mid level (from where they can
dribble down to the LLD) that solves the problem.

Doug Gilbert