On Tue, Feb 25, 2020 at 02:27:27PM +0100, Herbrechtsmeier Dr.-Ing. , Stefan wrote:

> would it be acceptable to add an additional function to the struct
> spi_controller which handle a transfer inside a NMI context or a panic? The
> new function will transfer data via register polling without any lock.

That would need to happen as part of a wider change that made it
possible to use such an interface safely and did so, off the top of my
head it's not immediately obvious how one would do that.  You'd need to
get the hardware into a sensible state and then do whatever needs doing
with some cooperation from the client driver in all this which is a bit
of an ask.  It's not a trivial bit of work, but I do see the use case
and it's absolutely valid.