Make exti an optional feature

* Add embassy-stm32 build with exti
* Add exti to examples

embassy-stm32/Cargo.toml

@@ -41,6 +41,7 @@ sdmmc-rs = ["embedded-sdmmc"]
 net = ["embassy-net", "vcell"]
 memory-x = ["stm32-metapac/memory-x"]
 subghz = []
+exti = []
 
 # Features starting with `_` are for internal use only. They're not intended
 # to be enabled by other crates, and are not covered by semver guarantees.

embassy-stm32/src/gpio.rs

@@ -480,6 +480,7 @@ pub(crate) mod sealed {
 }
 
 pub trait Pin: sealed::Pin + Sized {
+    #[cfg(feature = "exti")]
     type ExtiChannel: crate::exti::Channel;
 
     /// Number of the pin within the port (0..31)
@@ -527,6 +528,7 @@ impl AnyPin {
 
 unsafe_impl_unborrow!(AnyPin);
 impl Pin for AnyPin {
+    #[cfg(feature = "exti")]
     type ExtiChannel = crate::exti::AnyChannel;
 }
 impl sealed::Pin for AnyPin {
@@ -589,6 +591,7 @@ impl OptionalPin for NoPin {
 crate::pac::pins!(
     ($pin_name:ident, $port_name:ident, $port_num:expr, $pin_num:expr, $exti_ch:ident) => {
         impl Pin for peripherals::$pin_name {
+            #[cfg(feature = "exti")]
             type ExtiChannel = peripherals::$exti_ch;
         }
         impl sealed::Pin for peripherals::$pin_name {

embassy-stm32/src/lib.rs

@@ -33,7 +33,7 @@ pub mod dac;
 pub mod dcmi;
 #[cfg(all(eth, feature = "net"))]
 pub mod eth;
-#[cfg(exti)]
+#[cfg(feature = "exti")]
 pub mod exti;
 #[cfg(i2c)]
 pub mod i2c;
@@ -99,7 +99,7 @@ pub fn init(config: Config) -> Peripherals {
 
         gpio::init();
         dma::init();
-        #[cfg(exti)]
+        #[cfg(feature = "exti")]
         exti::init();
 
         rcc::init(config.rcc);