PCI: Add pci_irq_type() to query the allocated interrupt typegrafted

Add a helper that returns PCI_IRQ_MSIX, PCI_IRQ_MSI, or PCI_IRQ_INTX
based on the interrupt type the PCI core selected after
pci_alloc_irq_vectors().

Several drivers already open-code this check against pdev->msix_enabled
and pdev->msi_enabled, or even open code this helper [1].

A common helper avoids the duplication and keeps drivers from accessing
the bitfield directly (see also [2]).

Acked-by: Bjorn Helgaas <bhelgaas@google.com>
Tested-by: John Hubbard <jhubbard@nvidia.com>
Link: https://elixir.bootlin.com/linux/v7.1/source/drivers/net/ethernet/aquantia/atlantic/aq_pci_func.c#L196 [1]
Inspired-by: John Hubbard <jhubbard@nvidia.com>
Link: https://lore.kernel.org/all/DKKG2QM3YJYB.Z2H2B2UXJ75N@kernel.org/ [2]
Reviewed-by: Gary Guo <gary@garyguo.net>
Link: https://patch.msgid.link/20260813165234.620555-5-dakr@kernel.org
[ Add missing pci_irq_type() stub for CONFIG_PCI=n. ]
Signed-off-by: Danilo Krummrich <dakr@kernel.org>

1 files changed, 105 insertions, 0 deletions

diff --git a/rust/macros/vtable.rs b/rust/macros/vtable.rs
new file mode 100644
index 000000000..c6510b0c4
--- /dev/null
+++ b/rust/macros/vtable.rs
@@ -0,0 +1,105 @@
+// SPDX-License-Identifier: GPL-2.0
+
+use std::{
+    collections::HashSet,
+    iter::Extend, //
+};
+
+use proc_macro2::{
+    Ident,
+    TokenStream, //
+};
+use quote::ToTokens;
+use syn::{
+    parse_quote,
+    Error,
+    ImplItem,
+    Item,
+    ItemImpl,
+    ItemTrait,
+    Result,
+    TraitItem, //
+};
+
+fn handle_trait(mut item: ItemTrait) -> Result<ItemTrait> {
+    let mut gen_items = Vec::new();
+
+    gen_items.push(parse_quote! {
+         /// A marker to prevent implementors from forgetting to use [`#[vtable]`](vtable)
+         /// attribute when implementing this trait.
+         const USE_VTABLE_ATTR: ();
+    });
+
+    for item in &item.items {
+        if let TraitItem::Fn(fn_item) = item {
+            let name = &fn_item.sig.ident;
+            let gen_const_name = Ident::new(
+                &format!("HAS_{}", name.to_string().to_uppercase()),
+                name.span(),
+            );
+
+            // We don't know on the implementation-site whether a method is required or provided
+            // so we have to generate a const for all methods.
+            let cfg_attrs = crate::helpers::gather_cfg_attrs(&fn_item.attrs);
+            let comment =
+                format!("Indicates if the `{name}` method is overridden by the implementor.");
+            gen_items.push(parse_quote! {
+                #(#cfg_attrs)*
+                #[doc = #comment]
+                const #gen_const_name: bool = false;
+            });
+        }
+    }
+
+    item.items.extend(gen_items);
+    Ok(item)
+}
+
+fn handle_impl(mut item: ItemImpl) -> Result<ItemImpl> {
+    let mut gen_items = Vec::new();
+    let mut defined_consts = HashSet::new();
+
+    // Iterate over all user-defined constants to gather any possible explicit overrides.
+    for item in &item.items {
+        if let ImplItem::Const(const_item) = item {
+            defined_consts.insert(const_item.ident.clone());
+        }
+    }
+
+    gen_items.push(parse_quote! {
+        const USE_VTABLE_ATTR: () = ();
+    });
+
+    for item in &item.items {
+        if let ImplItem::Fn(fn_item) = item {
+            let name = &fn_item.sig.ident;
+            let gen_const_name = Ident::new(
+                &format!("HAS_{}", name.to_string().to_uppercase()),
+                name.span(),
+            );
+            // Skip if it's declared already -- this allows user override.
+            if defined_consts.contains(&gen_const_name) {
+                continue;
+            }
+            let cfg_attrs = crate::helpers::gather_cfg_attrs(&fn_item.attrs);
+            gen_items.push(parse_quote! {
+                #(#cfg_attrs)*
+                const #gen_const_name: bool = true;
+            });
+        }
+    }
+
+    item.items.extend(gen_items);
+    Ok(item)
+}
+
+pub(crate) fn vtable(input: Item) -> Result<TokenStream> {
+    match input {
+        Item::Trait(item) => Ok(handle_trait(item)?.into_token_stream()),
+        Item::Impl(item) => Ok(handle_impl(item)?.into_token_stream()),
+        _ => Err(Error::new_spanned(
+            input,
+            "`#[vtable]` attribute should only be applied to trait or impl block",
+        ))?,
+    }
+}