usb-storage: how to extend quirks flags to 64bit?

[Milan Broz]

Hello,

I tried to extend USB storage for the passthrough of Opal
security commands, and some adapters are clearly "not perfect".
I would need to introduce a new quirks flag to turn it off.

Seems that we are already out of quirks flags on 32bit
for usb storage - in usb_usual.h the last entry in mainline is
  US_FLAG(SENSE_AFTER_SYNC, 0x80000000)

Adding a new flag will work for 64-bit systems but not
for platforms with 32-bit unsigned long like i686.

How do we allow new flag definitions?

Struct us_data fflags can be made 64bit (defined in
drivers/usb/storage/usb.h), but the major problem is that these
are transferred through the generic driver_info field
defined in linux/mod_devicetable.h as unsigned long).
Making this 64bit is IMO an extensive API change (if even possible).
I guess this is not the way to go.

Could USB maintainers please help to advise what is the correct
solution? I am not familiar with the USB driver model here
and I see no easy way how it can be solved by a trivial static
allocation inside the USB storage driver.

Someone will need a new quirks flag in the future anyway... :)

Thanks,
Milan