On Sun, 29 Aug 2004, Cyril Scetbon wrote:
> I would like to know what are the signs which force you to add an
> UNUSUAL_DEV entry in unusual_devs.h ?
In the most general terms, you add an new unusual_devs entry when that's
what the usb-storage driver needs to work with the device! :-)
More specifically, each entry only contains a few pieces of information.
Adding a new entry will help only if those pieces are exactly what is
needed. Among the pieces are:
The fact that this is a Mass Storage device. Some devices don't
set their bInterfaceClass value to 0x08, so they aren't recognized
as Mass Storage devices. Adding an entry will cause them to be
recognized regardless.
The bInterfaceSubClass (US_SC_xxx) and bInterfaceProtocol
(US_PR_yyy) overrides. If a device gives the wrong value for
either of these, or uses 0xff to indicate vendor-specific, an
entry can override it to provide the right value.
The US_FL_zzz flags. Under 2.6 the usb-storage driver only uses
a few of those; the most common ones are US_FL_FIX_INQUIRY and
US_FL_FIX_CAPACITY. If the device doesn't respond properly to
the INQUIRY command (most devices have no trouble with this) or
responds to the READ CAPACITY command by giving its total number
of blocks rather than the last block number, these flags can
help.
Those are the only reasons for adding an unusual_devs entry for a device.
Alan Stern
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