MMC/Fuji: Media default rotation control is the rotation control is defined by specifications

David Burg daviburg at
Tue Apr 28 12:42:41 PDT 2009

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Our team is currently experiencing some challenging time understanding how to
make use of the write speed descriptors and in particular the write rotation
control field. The specs says:
"Media default rotation control is the rotation control is defined by media
Well, that is actually not so helpful as it fails to abstract the protocol
|from the media specifics, i.e. it requires the host to have specific
knowledge of the device / media. Then the MMC specification tries to be
helpful by adding a table of 'typical' default rotation controls.
What does 'typical' mean? Does it mean recommended but not mandatory and
really up to the media specification to say? Or it is a mandatory default
rotation control for the 'typical' media types listed in the table?
Furthermore the table is ambiguous is that it says 'DVD-R/-RW' but only
'DVD+RW'. What about DVD+R then? And do the entry cover only SL or is DL also
mandated by these entries?
The spec then says "If default rotation control is CAV, this field shall be
set to zero." - but there is not a single entry in the table where the
default rotation control is CAV. So this statement is quite weird. What
is/are the media for which the default rotation control is CAV?
Is there any way for the host to query what is the 'media default rotation
control' using MMC or Fuji?
With regards,

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