module!, license as an enum

[wcampbell0x2a]

Currently license is accepted as a byte string in the macro, but since the linux kernel only allows certain licenses, this could just be an enum.

Code:
/include/linux/module.h

 180   │ /*
 181   │  * The following license idents are currently accepted as indicating free
 182   │  * software modules
 183   │  *
 184   │  *  "GPL"               [GNU Public License v2]
 185   │  *  "GPL v2"            [GNU Public License v2]
 186   │  *  "GPL and additional rights" [GNU Public License v2 rights and more]
 187   │  *  "Dual BSD/GPL"          [GNU Public License v2
 188   │  *                   or BSD license choice]
 189   │  *  "Dual MIT/GPL"          [GNU Public License v2
 190   │  *                   or MIT license choice]
 191   │  *  "Dual MPL/GPL"          [GNU Public License v2
 192   │  *                   or Mozilla license choice]
 193   │  *
 194   │  * The following other idents are available
 195   │  *
 196   │  *  "Proprietary"           [Non free products]
 197   │  *
 198   │  * Both "GPL v2" and "GPL" (the latter also in dual licensed strings) are
 199   │  * merely stating that the module is licensed under the GPL v2, but are not
 200   │  * telling whether "GPL v2 only" or "GPL v2 or later". The reason why there
 201   │  * are two variants is a historic and failed attempt to convey more
 202   │  * information in the MODULE_LICENSE string. For module loading the
 203   │  * "only/or later" distinction is completely irrelevant and does neither
 204   │  * replace the proper license identifiers in the corresponding source file
 205   │  * nor amends them in any way. The sole purpose is to make the
 206   │  * 'Proprietary' flagging work and to refuse to bind symbols which are
 207   │  * exported with EXPORT_SYMBOL_GPL when a non free module is loaded.
 208   │  *
 209   │  * In the same way "BSD" is not a clear license information. It merely
 210   │  * states, that the module is licensed under one of the compatible BSD
 211   │  * license variants. The detailed and correct license information is again
 212   │  * to be found in the corresponding source files.
 213   │  *
 214   │  * There are dual licensed components, but when running with Linux it is the
 215   │  * GPL that is relevant so this is a non issue. Similarly LGPL linked with GPL
 216   │  * is a GPL combined work.
 217   │  *
 218   │  * This exists for several reasons
 219   │  * 1.   So modinfo can show license info for users wanting to vet their setup
 220   │  *  is free
 221   │  * 2.   So the community can ignore bug reports including proprietary modules
 222   │  * 3.   So vendors can do likewise based on their own policies
 223   │  */
 224   │ #define MODULE_LICENSE(_license) MODULE_FILE MODULE_INFO(license, _license)

Resulting in something like this:

  module! {
      type: RustMinimal,
      name: b"rust_minimal",
      author: "Rust for Linux Contributors",
      description: b"Rust minimal sample",
      license: License::GPLv2,
  }

[ojeda]

Given it is a proc macro, the interface may be anything we want. If we needed to process the license somehow in the Rust side, then I would agree.

An advantage of taking a string and forwarding it as-is (manually or through MODULE_LICENSE) is that we do not need to keep the C and Rust sides in sync. It is also closer to the C side (kernel developers may see it as an unneeded difference, i.e. it is not an enum either on the C side).

[ojeda]

Closing since no new comments came around.