From 9d37d15827e7ef1fe3ffdc847cdcd8ca2351be89 Mon Sep 17 00:00:00 2001
From: bjorn3 <17426603+bjorn3@users.noreply.github.com>
Date: Sun, 9 Jun 2024 18:14:18 +0200
Subject: [PATCH] pcid: Avoid duplicate read of vendor and device id

---
 pcid/src/pci_header.rs | 7 ++++---
 1 file changed, 4 insertions(+), 3 deletions(-)

diff --git a/pcid/src/pci_header.rs b/pcid/src/pci_header.rs
index 471f74b27c..95c960851a 100644
--- a/pcid/src/pci_header.rs
+++ b/pcid/src/pci_header.rs
@@ -42,12 +42,13 @@ impl PciHeader {
         access: &impl ConfigRegionAccess,
         addr: PciAddress,
     ) -> Result<PciHeader, PciHeaderError> {
-        if unsafe { access.read(addr, 0) } == 0xffffffff {
+        let header = TyPciHeader::new(addr);
+        let (vendor_id, device_id) = header.id(access);
+
+        if vendor_id == 0xffff && device_id == 0xffff {
             return Err(PciHeaderError::NoDevice);
         }
 
-        let header = TyPciHeader::new(addr);
-        let (vendor_id, device_id) = header.id(access);
         let (revision, class, subclass, interface) = header.revision_and_class(access);
         let header_type = header.header_type(access);
         let shared = SharedPciHeader {