[PATCH v2 1/2] rust: pci: remove TryFrom<&Device> implementation for &pci::Device

["Nicolás Antinori" <nico.antinori.7@gmail.com>]

Remove the `TryFrom<&device::Device<Ctx>>` implementation for
`&Device<Ctx>` since it has no remaining users.

This removal also eliminates a pre-existing lifetime soundness issue:
the input and output reference lifetimes were independent, allowing the
conversion of a temporarily borrowed `device::Device` into `&'static
pci::Device` in safe Rust. Removing the device could leave a dangling
reference.

Fixes: 7edc491f6fca ("drm: nova: Use nova-core to read VRAM_BAR_SIZE parameter")
Reported-by: Georgios Androutsopoulos <georgeandrout13@gmail.com>
Link: https://github.com/Rust-for-Linux/linux/issues/1264
Signed-off-by: Nicolás Antinori <nico.antinori.7@gmail.com>
---
 rust/helpers/pci.c |  5 -----
 rust/kernel/pci.rs | 21 ---------------------
 2 files changed, 26 deletions(-)

diff --git a/rust/helpers/pci.c b/rust/helpers/pci.c
index a8540f90b13c..3822b7f47c57 100644
--- a/rust/helpers/pci.c
+++ b/rust/helpers/pci.c
@@ -25,11 +25,6 @@ __rust_helper unsigned long rust_helper_pci_resource_flags(const struct pci_dev
 	return pci_resource_flags(pdev, bar);
 }

-__rust_helper bool rust_helper_dev_is_pci(const struct device *dev)
-{
-	return dev_is_pci(dev);
-}
-
 __rust_helper unsigned int rust_helper_pci_irq_type(struct pci_dev *pdev)
 {
 	return pci_irq_type(pdev);
diff --git a/rust/kernel/pci.rs b/rust/kernel/pci.rs
index 769d01d23429..0e9455fd544d 100644
--- a/rust/kernel/pci.rs
+++ b/rust/kernel/pci.rs
@@ -6,7 +6,6 @@

 use crate::{
     bindings,
-    container_of,
     device,
     device_id::{
         RawDeviceId,
@@ -535,26 +534,6 @@ fn as_ref(&self) -> &device::Device<Ctx> {
     }
 }

-impl<Ctx: device::DeviceContext> TryFrom<&device::Device<Ctx>> for &Device<Ctx> {
-    type Error = kernel::error::Error;
-
-    fn try_from(dev: &device::Device<Ctx>) -> Result<Self, Self::Error> {
-        // SAFETY: By the type invariant of `Device`, `dev.as_raw()` is a valid pointer to a
-        // `struct device`.
-        if !unsafe { bindings::dev_is_pci(dev.as_raw()) } {
-            return Err(EINVAL);
-        }
-
-        // SAFETY: We've just verified that the bus type of `dev` equals `bindings::pci_bus_type`,
-        // hence `dev` must be embedded in a valid `struct pci_dev` as guaranteed by the
-        // corresponding C code.
-        let pdev = unsafe { container_of!(dev.as_raw(), bindings::pci_dev, dev) };
-
-        // SAFETY: `pdev` is a valid pointer to a `struct pci_dev`.
-        Ok(unsafe { &*pdev.cast() })
-    }
-}
-
 // SAFETY: A `Device` is always reference-counted and can be released from any thread.
 unsafe impl Send for Device {}

--
2.47.3