rust: auxiliary: unregister on parent device unbind

Guarantee that an auxiliary driver will be unbound before its parent is
unbound; there is no point in operating an auxiliary device whose parent
has been unbound.

In practice, this guarantee allows us to assume that for a bound
auxiliary device, also the parent device is bound.

This is useful when an auxiliary driver calls into its parent, since it
allows the parent to directly access device resources and its device
private data due to the guaranteed bound device context.

Reviewed-by: Alice Ryhl <aliceryhl@google.com>
Reviewed-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Danilo Krummrich <dakr@kernel.org>

1 files changed, 5 insertions, 3 deletions

diff --git a/drivers/gpu/nova-core/driver.rs b/drivers/gpu/nova-core/driver.rs
index a83b86199182..ca0d5f8ad54b 100644
--- a/drivers/gpu/nova-core/driver.rs
+++ b/drivers/gpu/nova-core/driver.rs
@@ -3,6 +3,7 @@
 use kernel::{
     auxiliary, c_str,
     device::Core,
+    devres::Devres,
     pci,
     pci::{Class, ClassMask, Vendor},
     prelude::*,
@@ -16,7 +17,8 @@ use crate::gpu::Gpu;
 pub(crate) struct NovaCore {
     #[pin]
     pub(crate) gpu: Gpu,
-    _reg: auxiliary::Registration,
+    #[pin]
+    _reg: Devres<auxiliary::Registration>,
 }
 
 const BAR0_SIZE: usize = SZ_16M;
@@ -65,12 +67,12 @@ impl pci::Driver for NovaCore {
 
             Ok(try_pin_init!(Self {
                 gpu <- Gpu::new(pdev, bar.clone(), bar.access(pdev.as_ref())?),
-                _reg: auxiliary::Registration::new(
+                _reg <- auxiliary::Registration::new(
                     pdev.as_ref(),
                     c_str!("nova-drm"),
                     0, // TODO[XARR]: Once it lands, use XArray; for now we don't use the ID.
                     crate::MODULE_NAME
-                )?,
+                ),
             }))
         })
     }