[LSF/MM/BPF BOF] Userspace command abouts

[Sagi Grimberg]

>> I did not understand what is the relationship between aborts and CDL.
>> Sounds to me that this would tie in to something like Time Limited Error
>> Recovery (TLER) and LR bit set based on ioprio?
>>
>> I am unclear where do aborts come into play here.
> 
> CDL: Command Duration Limits
> 
> One use case is reading from storage for audio visual output.
> An application only wants to wait so long (e.g. one or two frames
> on the video output) before it wants to forget about the current
> read (i.e. "abort" it) and move onto the next read. An alert viewer
> might notice a momentary freeze frame.
> 
> The SCSI CDL mechanism uses the DL0, DL1 and DL2 bits in the READ(16,32)
> commands. CDL also depends on the CDLP and RWCDLP fields in the
> REPORT SUPPORTED OPERATION CODES command and one of the CDL
> mode pages. So there may be some additional "wiring" needed in the
> SCSI subsystem.

I still don't understand where issuing aborts from userspace come into
play here...