Re: [PATCH v3 0/9] gpu: nova-core: expose the logging buffers via debugfs

[Alice Ryhl <aliceryhl@google.com>]

On Wed, Dec 17, 2025 at 07:39:01PM -0600, Timur Tabi wrote:
> 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.
> 
> Based on Linus' repository, not drm-rust-next.
> 
> Summary of changes:
> 
> 1. Replace module_pci_driver! with explicit init function.
> 2. Creates root, per-gpu, and individual buffer debugfs entries.
> 3. Adds a pci::name() method to generate a PCI device name string.
> 4. Adds a lookup() method to debugfs, so that the root debugfs entry
>    doesn't need to be a global variable like it is in Nouveau.
> 5. Makes some updates to debugfs core code.
> 
> Alexandre Courbot (1):
>   gpu: nova-core: implement BinaryWriter for LogBuffer
> 
> Timur Tabi (8):
>   rust: pci: add PCI device name method
>   rust: debugfs: add lookup contructor
>   rust: debugfs: add Dir::empty() for no-op directory handle
>   rust: debugfs: fix Dir::scope() to not borrow self for returned
>     lifetime
>   gpu: nova-core: Replace module_pci_driver! with explicit module init
>   gpu: nova-core: create debugfs root when driver loads
>   gpu: nova-core: use pin projection in method boot()
>   gpu: nova-core: create GSP-RM logging buffers debugfs entries
> 
>  drivers/gpu/nova-core/gsp.rs       |  66 +++++++++++++++---
>  drivers/gpu/nova-core/gsp/boot.rs  |  15 ++--
>  drivers/gpu/nova-core/nova_core.rs |  29 +++++++-
>  rust/kernel/debugfs.rs             | 108 ++++++++++++++++++++++-------
>  rust/kernel/debugfs/entry.rs       |  49 ++++++++++++-
>  rust/kernel/pci.rs                 |  37 ++++++++++
>  6 files changed, 259 insertions(+), 45 deletions(-)

Adding Matthew as this touches debugfs.

Alice