Re: Pack of CAM improvements

On Sun, 24 Jan 2010 18:48:15 +0200
Alexander Motin <mav_at_FreeBSD.org> wrote:

> Gary Jennejohn wrote:
> > I started seeing a problem a few days ago with one of my DVD drives (a
> > burner at cd0) under 9-current, which makes it impossible to use it even
> > to simply read a DVD.
> > 
> > Here the (rather strange IMO) output in dmesg:
> > 
> > cd0: <HL-DT-ST DVD-RAM GSA-H54N 1.00> Removable CD-ROM SCSI-0 device
> > cd0: 66.700MB/s transfers (UDMA4, PIO size 65534bytes)
> > cd0: Attempt to query device size failed: UNIT ATTENTION, Power on, reset,
> > or bus device reset occurred
> > cd1 at ata0 bus 0 scbus6 target 1 lun 0
> > cd1: <TSSTcorp DVD-ROM SH-D162D SB01> Removable CD-ROM SCSI-0 device
> > cd1: 33.300MB/s transfers (UDMA2, PIO size 65534bytes)
> > cd1: Attempt to query device size failed: NOT READY, Medium not present -
> > tray closed
> > 
> > I haven't the foggiest why cd0 behaves diffrently from cd1, which is a
> > vanilla DVD drive and just works.
> 
> I am not sure yet what triggered these changes. May be just some timing
> issue. That UNIT ATTENTION seems reasonable, as reset indeed just
> happened there. The real problem is that CAM had several limitations in
> SCSI status handling, when working with ATAPI or USB devices. It made
> request processing stop in some cases, where retries would be expected.
> 
> New patch version should handle this and some other problems:
> http://people.freebsd.org/~mav/cam-ata.20100124.patch
> 
> Try it please. Thanks.
> 

This patch works extremely well!  Thanks.

---
Gary Jennejohn