A tiny simplification: now that FbLayout uses its own specific FbRange
type, add an FbRange.len() method, and use that to (very slightly)
simplify the calculation of Frts::frts_size initialization.

Suggested-by: Alexandre Courbot <acourbot@nvidia.com>
Reviewed-by: Gary Guo <gary@garyguo.net>
Signed-off-by: John Hubbard <jhubbard@nvidia.com>
---
 drivers/gpu/nova-core/fb.rs       | 6 ++++++
 drivers/gpu/nova-core/gsp/boot.rs | 2 +-
 2 files changed, 7 insertions(+), 1 deletion(-)

diff --git a/drivers/gpu/nova-core/fb.rs b/drivers/gpu/nova-core/fb.rs
index 6fb804c118c6..e803e6e0cdb9 100644
--- a/drivers/gpu/nova-core/fb.rs
+++ b/drivers/gpu/nova-core/fb.rs
@@ -100,6 +100,12 @@ pub(crate) fn unregister(&self, bar: &Bar0) {
 
 pub(crate) struct FbRange(Range<u64>);
 
+impl FbRange {
+    pub(crate) fn len(&self) -> u64 {
+        self.0.end - self.0.start
+    }
+}
+
 impl From<Range<u64>> for FbRange {
     fn from(range: Range<u64>) -> Self {
         Self(range)
diff --git a/drivers/gpu/nova-core/gsp/boot.rs b/drivers/gpu/nova-core/gsp/boot.rs
index be427fe26a58..036a42a6afb6 100644
--- a/drivers/gpu/nova-core/gsp/boot.rs
+++ b/drivers/gpu/nova-core/gsp/boot.rs
@@ -70,7 +70,7 @@ fn run_fwsec_frts(
             bios,
             FwsecCommand::Frts {
                 frts_addr: fb_layout.frts.start,
-                frts_size: fb_layout.frts.end - fb_layout.frts.start,
+                frts_size: fb_layout.frts.len(),
             },
         )?;
 
-- 
2.52.0