RfL currently does not integrate very well with some Kconfigs

[Philipp Stanner <pstanner@redhat.com>]

Recently, I've been trying to accomplish some work on the rust-pci
branch in RfL.

I like to base my configs on an allnoconfig to get only the stuff I
really need.

Doing
make LLVM=1 allnoconfig && make LLVM=1 menuconfig
activating only 64-Bit and Rust already generates build-errors, for
example:

error[E0412]: cannot find type `dma_pool` in crate `bindings`
  --> rust/kernel/dma.rs:74:25
   |
74 |     ptr: *mut bindings::dma_pool,
   |                         ^^^^^^^^ not found in `bindings`

error[E0425]: cannot find function `dma_pool_create` in crate
`bindings`
  --> rust/kernel/dma.rs:92:23
   |
92 |             bindings::dma_pool_create(name.as_char_ptr(),
dev.raw_device(), size, align, boundary)
   |                       ^^^^^^^^^^^^^^^ not found in `bindings`

error[E0425]: cannot find function `dma_pool_alloc` in crate `bindings`
   --> rust/kernel/dma.rs:116:38
    |
116 |         let ptr = unsafe { bindings::dma_pool_alloc(self.ptr,
flags, &mut dma_handle) };
    |                                      ^^^^^^^^^^^^^^ not found in
`bindings`

error[E0412]: cannot find type `dma_pool` in crate `bindings`
   --> rust/kernel/dma.rs:136:42
    |
136 |     type AllocationData = *mut bindings::dma_pool;
    |                                          ^^^^^^^^ not found in
`bindings`



Switching on PCI, but not PCI's MSI, causes other errors, such as:

  RUSTC L rust/uapi.o
  EXPORTS rust/exports_alloc_generated.h
  EXPORTS rust/exports_bindings_generated.h
  RUSTC L rust/kernel.o
error[E0425]: cannot find function `pci_alloc_irq_vectors_affinity` in
crate `bindings`
   --> rust/kernel/pci.rs:289:23
    |
289 |             bindings::pci_alloc_irq_vectors_affinity(
    |                       ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ not found in
`bindings`

Strong suspect for the cause is that this function is defined as part
of MSI, so just activating PCI doesn't suffice.

I verified that this is indeed a config problem. The entire toolchain
is installed according to the official documentation, selecting that
one compiler version that currently works etc.

Setting PCI + MSI (and, in Hacking, Rust Hacking -> Allow unoptimized
build-time assertations) results in a valid build.


So, it would seem there are some "deponds on" entries missing
somewhere.
Is this problem known? Any plans or suggestions how to deal with it?

My instinct tells me that there could be many potentially broken
configs out there.


Regards,
P.