Add a default method to `CommandToGsp` which computes the size of a
command.

Tested-by: Zhi Wang <zhiw@nvidia.com>
Signed-off-by: Eliot Courtney <ecourtney@nvidia.com>
---
 drivers/gpu/nova-core/gsp/cmdq.rs | 12 +++++++++---
 1 file changed, 9 insertions(+), 3 deletions(-)

diff --git a/drivers/gpu/nova-core/gsp/cmdq.rs b/drivers/gpu/nova-core/gsp/cmdq.rs
index b41a866e24da..861f5666fe7f 100644
--- a/drivers/gpu/nova-core/gsp/cmdq.rs
+++ b/drivers/gpu/nova-core/gsp/cmdq.rs
@@ -94,6 +94,12 @@ fn init_variable_payload(
     ) -> Result {
         Ok(())
     }
+
+    /// Total size of the command (including its variable-length payload) without the
+    /// [`GspMsgElement`] header.
+    fn size(&self) -> usize {
+        size_of::<Self::Command>() + self.variable_payload_len()
+    }
 }
 
 /// Trait representing messages received from the GSP.
@@ -529,10 +535,10 @@ pub(crate) fn send_command<M>(&mut self, bar: &Bar0, command: M) -> Result
         // This allows all error types, including `Infallible`, to be used for `M::InitError`.
         Error: From<M::InitError>,
     {
-        let command_size = size_of::<M::Command>() + command.variable_payload_len();
+        let size_in_bytes = command.size();
         let dst = self
             .gsp_mem
-            .allocate_command(command_size, Self::ALLOCATE_TIMEOUT)?;
+            .allocate_command(size_in_bytes, Self::ALLOCATE_TIMEOUT)?;
 
         // Extract area for the command itself. The GSP message header and the command header
         // together are guaranteed to fit entirely into a single page, so it's ok to only look
@@ -540,7 +546,7 @@ pub(crate) fn send_command<M>(&mut self, bar: &Bar0, command: M) -> Result
         let (cmd, payload_1) = M::Command::from_bytes_mut_prefix(dst.contents.0).ok_or(EIO)?;
 
         // Fill the header and command in-place.
-        let msg_element = GspMsgElement::init(self.seq, command_size, M::FUNCTION);
+        let msg_element = GspMsgElement::init(self.seq, size_in_bytes, M::FUNCTION);
         // SAFETY: `msg_header` and `cmd` are valid references, and not touched if the initializer
         // fails.
         unsafe {

-- 
2.53.0