sd_read_cache_type

[Andries.Brouwer@cwi.nl]

Last year I wrote half a dozen drivers for various USB card readers.
Some don't work anymore with 2.5.recent.
I just investigated one. The reason it stopped working is the
  sd_read_cache_type()
call added in 2.5.41. (With that call removed it works again.)

Will look a bit more at the details later.
For now a question: this call does a MODE_SENSE with the DBD
(disable block descriptors) bit set. Is there a reason for that?
Wouldn't the same code work in the same way without that bit?

And the reason I ask is that we already have sd_do_mode_sense6(),
so part of sd_read_cache_type() can be simply replaced by a call
of sd_do_mode_sense6(), but the latter needs an extra parameter
if DBD is really needed.

And a second question: sd_read_cache_type() is called also
when no medium is present. Objections against only calling
when media are present?

Andries