drm/panic: Add a qr_code panic screen

This series adds a new panic screen, with the kmsg data embedded in a QR-code.

The main advantage of QR-code, is that you can copy/paste the debug data to a bug report.

The QR-code encoder is written in rust, and is very specific to drm_panic.
The reason is that it is called in a panic handler, and thus can't allocate memory, or use locking.
The rust code uses a few rust core API, and provides only two C entry points.
There is no particular reason to do it in rust, I just wanted to learn rust, and see if it can work in the kernel.

If you want to see what it looks like, I've put a few screenshots here:
https://github.com/kdj0c/panic_report/issues/1

v2:
 * Rewrite the rust comments with Markdown (Alice Ryhl)
 * Mark drm_panic_qr_generate() as unsafe (Alice Ryhl)
 * Use CStr directly, and remove the call to as_str_unchecked()
   (Alice Ryhl)
 * Add a check for data_len <= data_size (Greg KH)

Jocelyn Falempe (4):
  drm/panic: Add integer scaling to blit()
  drm/rect: add drm_rect_overlap()
  drm/panic: simplify logo handling
  drm/panic: Add a qr_code panic screen

 drivers/gpu/drm/Kconfig         |   29 +
 drivers/gpu/drm/Makefile        |    1 +
 drivers/gpu/drm/drm_drv.c       |    3 +
 drivers/gpu/drm/drm_panic.c     |  338 +++++++++--
 drivers/gpu/drm/drm_panic_qr.rs | 1004 +++++++++++++++++++++++++++++++
 include/drm/drm_panic.h         |    4 +
 include/drm/drm_rect.h          |   15 +
 7 files changed, 1355 insertions(+), 39 deletions(-)
 create mode 100644 drivers/gpu/drm/drm_panic_qr.rs


base-commit: 5a716b06b329bd2108c95a4f04c71bbe491729f2
-- 
2.45.2