cam patch: reducing logging output for 'normal' failures

[Alexander Motin]

Bruce Cran wrote:
> I came across http://www.freebsd.org/cgi/query-pr.cgi?pr=kern/119668
> which contains a patch to reduce the verbosity of output from the cam
> subsystem. cam has a tendancy to be a bit spammy when it 
> comes across fairly normal situations such as the tray having been left 
> open, or there just not being a disc present. For example:
> 
> (probe0:umass-sim0:0:0:0): TEST UNIT READY. CDB: 0 0 0 0 0 0 
> (probe0:umass-sim0:0:0:0): CAM status: SCSI Status Error
> (probe0:umass-sim0:0:0:0): SCSI status: Check Condition
> (probe0:umass-sim0:0:0:0): SCSI sense: NOT READY asc:3a,1 (Medium not present - tray closed)
> cd0 at umass-sim0 bus 0 scbus9 target 0 lun 0
> cd0: <DVDRW USB H16X B02T> Removable CD-ROM SCSI-0 device 
> cd0: 40.000MB/s transfers
> cd0: Attempt to query device size failed: NOT READY, Medium not present
> - tray closed
> 
> The first message, "Medium not present - tray closed" is unnecessary 
> since it's repeated a few lines later and can look as though 
> there's a real problem. I've attached an updated patch which adds the 
> the tray open warning too.
> 
> Any comments?

I have feeling that it could depend on consumer: whether it wants kernel
should log it's errors or not. For example, it could be reasonable to
log errors for kernel drivers not doing it by themselves, such as "ad"
or "ada" (another question why they couldn't do it). Same time it is
probably impractical to log errors for requests coming from user-level
via "pass" driver.

-- 
Alexander Motin