gpu: nova-core: expose the logging buffers via debugfs

GSP-RM writes its printf message to "logging buffers", which are blocks
memory allocated by the driver.  The messages are encoded, so exposing
the buffers as debugfs entries allows the buffers to be extracted and
decoded by a special application.

When the driver loads, a /sys/kernel/debug/nova_core root entry is
created.  To do this, the normal module_pci_driver! macro call is
replaced with an explicit initialization function, as this allows
that debugfs entry to be created once for all GPUs.

Then in each GPU's initialization, a subdirectory based on the PCI
BDF name is created, and the logging buffer entries are created under
that.

Note: the debugfs entry has a file size of 0, because debugfs defaults
a 0 size and the Rust abstractions do not adjust it for the same of
the object.  Nouveau makes this adjustment manually in the driver.

Changes since v3:
1. Implement a LookupDir struct instead of adding lookup methods to Dir.
2. Adds a Directory trait that is implemented by both LookupDir and Dir.
3. Creates DynParent enum to wrap both LookupDir and Dir.
4. No longer tries to "fix" Scope or scoped_dir.

Alexandre Courbot (1):
  gpu: nova-core: implement BinaryWriter for LogBuffer

Timur Tabi (8):
  rust: pci: add PCI device name method
  gpu: nova-core: Replace module_pci_driver! with explicit module init
  gpu: nova-core: use pin projection in method boot()
  rust: debugfs: implement Directory trait for Dir
  rust: debugfs: wrap Entry in an enum to prep for LookupDir
  rust: debugfs: add LookupDir
  gpu: nova-core: create debugfs root when driver loads
  gpu: nova-core: create GSP-RM logging buffers debugfs entries

 drivers/gpu/nova-core/gsp.rs       |  68 +++++++++++--
 drivers/gpu/nova-core/gsp/boot.rs  |  14 +--
 drivers/gpu/nova-core/nova_core.rs |  32 ++++++-
 rust/kernel/debugfs.rs             | 148 ++++++++++++++++++++++++++++-
 rust/kernel/debugfs/entry.rs       | 100 ++++++++++++++++++-
 rust/kernel/pci.rs                 |  37 ++++++++
 6 files changed, 377 insertions(+), 22 deletions(-)


base-commit: 654826aa4a8f25cf825ad9254f37e6cb5092098f
-- 
2.52.0