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HEADS UP: SCSI device specific timeouts


I just committed fetching device specific timeout values from SCSI devices.

The benefit is that we do not abort a perfectly running SCSI commands with device reset before its device provided timeout and thus gain
more reliability with slower devices.

The timeout values are loaded at attachment time if the device supports them, If the timeout information is available it shows up as "timeout-info" in dmesg like this:

st0 at scsibus0 target 9 lun 0: <IBM, ULTRIUM-HH7, J4D1> tape removable timeout-info
st0: density code 92, variable blocks, write-enabled

This mechanism is disabled for USB umass devices as some of these may get into strange
states when the SCSI command is sent.

The code has been tested with SCSI tapes, changers and disks. The newer tapes provide the timeout information and thus some helpful longer timeouts like TUR 60 sec instead of our default of 15 sec and WRITE ~1500 sec instead of 120 sec.

So, if anything gets now stuck at SCSI attachment time it might be the new MAINTENANCE_IN/REPORT_SUPPORTED_OPCODES query and thus might just need a quirk. Hopefully there are not many of these devices.

Best regards,

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