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DragonFly users List (threaded) for 2005-04
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Re: boot loader question

From: Bill Hacker <wbh@xxxxxxxxxxxxx>
Date: Tue, 05 Apr 2005 04:30:47 +0800

Peter Hessler wrote:

On Tue, 05 Apr 2005 02:50:17 +0800
Bill Hacker <wbh@xxxxxxxxxxxxx> wrote:

: : BTW - a USB-attached device *may* show up as '/dev/da(n)' - claiming to
: be a SCSI. Go figure.....

The reason for that, is the USB bus presents it as a SCSI device. But many
devices do the emulation improperly, so there are all sorts of nasty quirks and
workarounds in umass code. :/

Nearly *all* of the USB devices do the emulation 'improperly' - even as to a 'proper subset' of SCSI.

Look at what is out there: Largely memory devices factory-formatted as FAT.

PCMCIA/Cardbus at least presents itself 'honestly' - take a CF formatted as a FAT HDD.
- looks like any other IDE/ATAPI device to the OS, as it should - that's what the hardware bus *is*.

Put essentially the same RAM on a USB stick and it gets uppity, lies about its provenance, and starts making trouble.

Given the actual wiring and the 'logical' protocols it would have made better sense for it to emulate an ethernet NAS (ignore the physical layer) or an RS-485 serial 'bus' attached device (acknowledge the physical layer).

As with 'Aloha' or Ethernet, we are fortunate USB can be made to work at all, let alone as well as it (usually) does.

Verdammt compromises... :-(


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