Hello.
Alan Stern wrote:
Best guess (and it's a guess only) would be that the USB bridge SAT
layer doesn't implement ATA_16 and so fails in interesting ways when it
comes in. Does the ATA_12 version of IDENTIFY DEVICE succeed?
It does. And in between the two is an ATA_16 SET FEATURES command
which also (apparently) succeeds. That is, there is no error
indication from the device -- but goodness knows if it actually carries
out the command.
Incidentally, there's a discussion of this problem with input from an
engineer at the company that makes the bridge chip here:
https://bugs.launchpad.net/ubuntu/+source/linux-fsl-imx51/+bug/431963
See comment #25 and later. He claims that the ATA pass-through command
contains a SECTOR COUNT field of 0 even though it asks for 512 bytes of
IDENTIFY data. This invalid parameter combination causes the bridge
chip to get confused, and instead of failing gracefully, it messes up
the USB protocol.
IDENTIFY DEVICE command always returns 512 bytes of data, regardless
of any value in the sector count register.
Does anybody know where to find out why hdparm is sending an IDENTIFY
command with invalid parameters?
IDENTIFY DEVICE command has *no* parameters.
Alan Stern
WBR, Sergei
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