fix: correct BAR size probing for non-zero base addresses

The previous BAR size calculation used !(inverted & mask) & mask which\nproduces incorrect results when the BAR has a non-zero base address.\nUse lowest-set-bit extraction (masked & (!masked + 1)) to correctly\ncompute the BAR size from the writable bit pattern read back from hardware.

local/recipes/drivers/redox-driver-sys/source/src/pci.rs

@@ -574,11 +574,16 @@ impl PciDevice {
         let is_io = (original & 0x01) != 0;
         let mask = if is_io { 0xFFFFFFFC } else { 0xFFFFFFF0 };
 
-        let size_val = !(inverted & mask) & mask;
-        if size_val == 0 {
+        let masked = inverted & mask;
+        if masked == 0 {
             return Ok(0);
         }
-        Ok(size_val as u64)
+        // The lowest set bit in the readback IS the BAR size.
+        // This correctly handles non-zero base addresses because
+        // writable address bits above the size boundary are all 1s
+        // while hardwired size bits below are all 0s.
+        let size = masked & (!masked).wrapping_add(1);
+        Ok(size as u64)
     }
 
     fn probe_bar64_size(&mut self, offset: u64) -> Result<u64> {
@@ -594,14 +599,16 @@ impl PciDevice {
         self.write_config_dword(offset, original_lo)?;
         self.write_config_dword(offset + 4, original_hi)?;
 
-        let lo = !(inverted_lo & 0xFFFFFFF0) & 0xFFFFFFF0;
-        let hi = !inverted_hi;
+        let masked_lo = inverted_lo & 0xFFFFFFF0;
+        let masked_hi = inverted_hi;
+        let masked = ((masked_hi as u64) << 32) | (masked_lo as u64);
 
-        if lo == 0 && hi == 0 {
+        if masked == 0 {
             return Ok(0);
         }
 
-        let size = ((hi as u64) << 32) | (lo as u64);
+        // The lowest set bit in the readback IS the BAR size.
+        let size = masked & (!masked).wrapping_add(1);
         Ok(size)
     }