pci: clearer intersection code

Author: zyuiop

src/arch/x86_64/kernel/pci.rs

@@ -94,7 +94,6 @@ pub(crate) fn init() {
 	}
 
 	// For Hermit, we currently limit scanning to the first 32 buses.
-	const PCI_MAX_BUS_NUMBER: u8 = 32;
 	scan_bus(
 		0..PCI_MAX_BUS_NUMBER,
 		PciConfigRegion::Pci(LegacyPciConfigRegion::new()),
@@ -126,7 +125,7 @@ fn scan_bus(bus_range: impl IntoIterator<Item = u8> + Debug, pci_config: PciConf
 #[cfg(feature = "acpi")]
 mod pcie {
 	use core::{ptr, slice};
-
+	use core::ops::{Bound, IntoBounds, RangeBounds};
 	use memory_addresses::{PhysAddr, VirtAddr};
 	use pci_types::{ConfigRegionAccess, PciAddress};
 
@@ -196,6 +195,7 @@ mod pcie {
 			// We go through `pci_config_space_address`, which makes sure the physical addresses are valid
 			let pci_start = self.pci_config_space_address(0, 0, 0).as_u64();
 			let pci_end = self.pci_config_space_address(PCI_MAX_BUS_NUMBER, u8::MAX, u8::MAX).as_u64() + 0x1000;
+			let pci_range = pci_start..pci_end;
 
 			let all_memory_regions = fdt
 				.find_all_nodes("/memory")
@@ -204,13 +204,11 @@ mod pcie {
 			for mem_region in all_memory_regions {
 				let region_start = u64::try_from(mem_region.starting_address.addr()).unwrap();
 				let region_end = region_start + u64::try_from(mem_region.size.expect("found a memory region with no declared size")).unwrap();
+				let region_range = region_start..region_end;
 
-				if
-					(pci_start >= region_start && pci_start <= region_end) // PCI region starts within the memory region
-					|| (pci_end >= region_start && pci_end <= region_end) // PCI region ends within the memory region
-					|| (pci_start <= region_start && pci_end >= region_end) // PCI region contains the memory region
-				{
-					error!("The declared PCI region {pci_start:x}-{pci_end:x} may overlap with physical memory region {region_start:x}-{region_end:x}");
+				let intersection = region_range.intersect(pci_range);
+				if !intersection.is_empty() {
+					error!("The declared PCI region {pci_start:x}-{pci_end:x} overlaps with physical memory region {region_start:x}-{region_end:x}. Intersection: {intersection:?}");
 					return false;
 				}
 			}

src/lib.rs

@@ -66,6 +66,8 @@
 	),
 	feature(thread_local)
 )]
+#![cfg_attr(feature = "acpi", feature(range_bounds_is_empty))]
+#![cfg_attr(feature = "acpi", feature(range_into_bounds))]
 #![cfg_attr(target_os = "none", no_std)]
 #![cfg_attr(target_os = "none", feature(custom_test_frameworks))]
 #![cfg_attr(all(target_os = "none", test), test_runner(crate::test_runner))]