Re: [usb-storage] Time to allow MODE SENSE for USB disk-type storag edevices?

[Pat LaVarre <p.lavarre@ieee.org>]

> > res = sd_do_mode_sense(SRpnt, 0, 0x3F, buffer, 4, &data);

I see the structure of this code arbitrarily requires H = C.  That
structure makes sense only when H = D <= C.  Why we guess D <= C when C
is 4, I do not understand.

> * First attempt: ask for all pages (0x3F), ...

I hear Windows starts with page x08, not x3F.

> all pages (0x3F), but only 4 bytes.

SCSI Pass-Through Mode Sense Command May Crash the Computer
http://support.microsoft.com/?kbid=813908

suggests Talk-like-Windows excludes 4 bytes, by saying -i 4 -y "1A
xx:xx:xx 04 00" crashes the Win 2K kernel for much Atapi, just as -y "12
00:00:00 00 00" crashes some lk for much Usb.

> some devices hang if we ask for more than is available.

Also some hosts hang when D < H.

Offline recently I received an as yet unconfirmed report that 2.4.25
ioctl CDROM_SEND_PACKET fails (but does not hang) when D < H.

> ... my devices ... work...

Yes, here we choose among evils.

If Windows doesn't discover PDT x00/0E writability except by trying to
write blocks, then any other technique we invent will fail to
interoperate broadly.

Pat LaVarre