[meta-freescale] about freescale dvd-rom

[Thomas Schmitt]

Hi,

first let me state that i am the upstream developer of
libburn, not of cdrtools. :)

Since a few weeks i am watching Lian jianfei's woes with
Linux DVD burning tools.
We used libburn's SCSI logging facility to learn about
the SCSI passthrough traffic between burn program and
DVD drive.

On imx6q board quite frequently, on another ARM based board
much less often, there are glitches to see with the reply
data from the DVD burner.
The imx6q board quite often produces underneath ioctl(SG_IO)
either a userspace SIGSEGV or memory corruption alerts.

But only if board and DVD burner are connected SATA to SATA.

See also
https://lists.yoctoproject.org/pipermail/meta-freescale/2014-July/009648.html
(The suspicion that the correct reply would be put
 to the wrong address is disproved meanwhile. The
 reply buffer sg_io_hdr_t.dxferp contains all zeros
 before ioctl(SG_IO) and non-zero nonsense afterwards.)


All problems vanish, as soon as a SATA-USB bridge is attached
to the DVD burner and the traffic runs over an USB port of
the imx6q board.

I never got reports about such problems with Linux on i386
or amd64. So i assume it has something to do with the SATA
controller on the board and/or the according driver in the
kernel.


Have a nice day :)

Thomas