hal: rename subsytems() to as_mut()

diff --git a/src/rust/bitbox-hal/src/lib.rs b/src/rust/bitbox-hal/src/lib.rs
index 9620e3d..90c9473 100644
--- a/src/rust/bitbox-hal/src/lib.rs
+++ b/src/rust/bitbox-hal/src/lib.rs
@@ -44,7 +44,7 @@ pub trait Hal {
     type Memory: memory::Memory;
     type System: system::System;
 
-    fn subsystems(
+    fn as_mut(
         &mut self,
     ) -> HalSubsystems<
         '_,
@@ -57,26 +57,26 @@ pub trait Hal {
     >;
 
     fn ui(&mut self) -> &mut Self::Ui {
-        self.subsystems().ui
+        self.as_mut().ui
     }
 
     fn random(&mut self) -> &mut Self::Random {
-        self.subsystems().random
+        self.as_mut().random
     }
 
     fn sd(&mut self) -> &mut Self::Sd {
-        self.subsystems().sd
+        self.as_mut().sd
     }
 
     fn securechip(&mut self) -> &mut Self::SecureChip {
-        self.subsystems().securechip
+        self.as_mut().securechip
     }
 
     fn memory(&mut self) -> &mut Self::Memory {
-        self.subsystems().memory
+        self.as_mut().memory
     }
 
     fn system(&mut self) -> &mut Self::System {
-        self.subsystems().system
+        self.as_mut().system
     }
 }
diff --git a/src/rust/bitbox02-rust/src/hal/testing.rs b/src/rust/bitbox02-rust/src/hal/testing.rs
index 6844f9a..a2d6848 100644
--- a/src/rust/bitbox02-rust/src/hal/testing.rs
+++ b/src/rust/bitbox02-rust/src/hal/testing.rs
@@ -44,7 +44,7 @@ impl<'a> crate::hal::Hal for TestingHal<'a> {
     type Memory = TestingMemory;
     type System = TestingSystem;
 
-    fn subsystems(
+    fn as_mut(
         &mut self,
     ) -> crate::hal::HalSubsystems<
         '_,
diff --git a/src/rust/bitbox02-rust/src/hww/api/bip85.rs b/src/rust/bitbox02-rust/src/hww/api/bip85.rs
index 7be2445..0a9e554 100644
--- a/src/rust/bitbox02-rust/src/hww/api/bip85.rs
+++ b/src/rust/bitbox02-rust/src/hww/api/bip85.rs
@@ -111,7 +111,7 @@ async fn process_bip39(hal: &mut impl crate::hal::Hal) -> Result<(), Error> {
     let mnemonic = keystore::bip85_bip39(hal, num_words, index)?;
     let words: Vec<&str> = mnemonic.split(' ').collect();
     {
-        let crate::hal::HalSubsystems { ui, random, .. } = hal.subsystems();
+        let crate::hal::HalSubsystems { ui, random, .. } = hal.as_mut();
         crate::workflow::mnemonic::show_and_confirm_mnemonic(ui, random, &words).await?;
     }
 
diff --git a/src/rust/bitbox02-rust/src/hww/api/show_mnemonic.rs b/src/rust/bitbox02-rust/src/hww/api/show_mnemonic.rs
index 4ae08d6..dec00c2 100644
--- a/src/rust/bitbox02-rust/src/hww/api/show_mnemonic.rs
+++ b/src/rust/bitbox02-rust/src/hww/api/show_mnemonic.rs
@@ -47,7 +47,7 @@ pub async fn process(hal: &mut impl crate::hal::Hal) -> Result<Response, Error>
     let words: Vec<&str> = mnemonic_sentence.split(' ').collect();
 
     {
-        let crate::hal::HalSubsystems { ui, random, .. } = hal.subsystems();
+        let crate::hal::HalSubsystems { ui, random, .. } = hal.as_mut();
         crate::workflow::mnemonic::show_and_confirm_mnemonic(ui, random, &words).await?;
     }
 
diff --git a/src/rust/bitbox02-rust/src/keystore.rs b/src/rust/bitbox02-rust/src/keystore.rs
index b1d4bc1..06c2e80 100644
--- a/src/rust/bitbox02-rust/src/keystore.rs
+++ b/src/rust/bitbox02-rust/src/keystore.rs
@@ -55,8 +55,13 @@ impl<'a, M: Memory, R: Random, S: SecureChip> KeystoreHalImpl<'a, M, R, S> {
     where
         H: crate::hal::Hal<Memory = M, Random = R, SecureChip = S>,
     {
-        let subsystems = hal.subsystems();
-        Self::new(subsystems.memory, subsystems.random, subsystems.securechip)
+        let crate::hal::HalSubsystems {
+            random,
+            securechip,
+            memory,
+            ..
+        } = hal.as_mut();
+        Self::new(memory, random, securechip)
     }
 }
 
diff --git a/src/rust/bitbox02-rust/src/workflow/unlock.rs b/src/rust/bitbox02-rust/src/workflow/unlock.rs
index e019ea3..8683d53 100644
--- a/src/rust/bitbox02-rust/src/workflow/unlock.rs
+++ b/src/rust/bitbox02-rust/src/workflow/unlock.rs
@@ -162,7 +162,7 @@ pub async fn unlock_bip39(hal: &mut impl crate::hal::Hal, seed: &[u8]) {
         securechip,
         memory,
         ..
-    } = hal.subsystems();
+    } = hal.as_mut();
     let mut keystore_hal = crate::keystore::KeystoreHalImpl::new(memory, random, securechip);
 
     let ((), result) = futures_lite::future::zip(
diff --git a/src/rust/bitbox02/src/hal.rs b/src/rust/bitbox02/src/hal.rs
index 9067d26..c1ad3be 100644
--- a/src/rust/bitbox02/src/hal.rs
+++ b/src/rust/bitbox02/src/hal.rs
@@ -43,7 +43,7 @@ impl Hal for BitBox02Hal {
     type Memory = memory::BitBox02Memory;
     type System = system::BitBox02System;
 
-    fn subsystems(
+    fn as_mut(
         &mut self,
     ) -> bitbox_hal::HalSubsystems<
         '_,