feat(hal): implement PWM peripheral with dual-platform support

CMakeLists.txt

@@ -54,8 +54,9 @@ if(EOS_BUILD_TESTS AND NOT EOS_PRODUCT)
         EOS_ENABLE_SENSOR=1
         EOS_ENABLE_FILESYSTEM=1
         EOS_ENABLE_MOTOR_CTRL=1
+        EOS_ENABLE_PWM=1
     )
-    message(STATUS "  Test features: multicore net power ota sensor filesystem motor_ctrl")
+    message(STATUS "  Test features: multicore net power ota sensor filesystem motor_ctrl pwm")
 endif()
 
 # Global include for eos_config.h and product profiles
@@ -70,6 +71,7 @@ include_directories(
 add_library(eos_hal STATIC
     hal/src/hal_common.c
     hal/src/hal_extended_stubs.c
+    hal/src/hal_pwm.c
 )
 
 # Which backend source is compiled, and which one eos_hal_init() falls back to,

STATUS.md

@@ -35,7 +35,8 @@ is an admission of an unmeasured claim, and should be driven to zero.
 | Kernel (task, sync, ipc, multicore, heap) | `libeos_kernel.a` | Experimental | Builds host and Cortex-M4; `test_kernel` passes. Mutex priority inheritance is transitive and recomputed from an invariant. No preemption or latency measurement. |
 | HAL — dispatch layer | `libeos_hal.a` | Experimental | `hal_common.c` dispatches to a registered backend; `test_drivers` passes. |
 | HAL — host backend | (in `libeos_hal.a`) | **Planned** | `hal_linux.c` implements a Linux backend, but `eos_hal_linux_register()` is **never called and is declared in no public header**. On a host build no backend registers, `eos_hal_init()` returns `-1`, and every HAL call silently no-ops. |
-| HAL — extended peripherals (ADC, PWM, I²C, SPI, …) | (in `libeos_hal.a`) | **Planned** | `hal_extended_stubs.c` is 740 of the HAL's 3,185 lines and contains 144 `(void)param;` casts. The API exists; the peripherals do not. |
+| HAL — extended peripherals (host) | (in `libeos_hal.a`) | Experimental | `hal_extended_stubs.c` is 707 lines and contains 268 `(void)param;` casts; ADC, I²C, SPI and most other extended peripherals remain stub-only. PWM now has a real host backend (`hal_pwm.c`) — a state-recording stub, not a waveform generator — with `test_pwm` **28/28 pass**. |
+| HAL — extended peripherals (STM32F4) | (in `libeos_hal.a`, cross build) | **Planned** | PWM and ADC each have STM32F4 register-level code (`hal_pwm.c`, `hal_extended.c`), but neither is compiled by any build target in this repository: the ARM CI job (`.github/workflows/build.yml`) compiles an explicit source list that omits both files, and the CMake cross-build (`toolchains/arm-cortex-m4.cmake`) sets `EOS_MCU_STM32F4` as a cache variable that is never converted into a compiler `-D` flag either. No test exercises this code, and no ADC test exists at all. |
 | Architecture — ARM Cortex-M4 / R5 | 23 `.a` targets | Experimental | Cross-compiles clean via `arm-cortex-m4`, `arm-none-eabi-stm32f4` and `arm-none-eabi-r5`; artifacts verified `armv7e-m` / `armv7` with `objdump -f`. **Never executed** — no board, no QEMU. |
 | Architecture — RISC-V, Cortex-A/AArch64 | — | **Unknown** | Toolchain files exist (`riscv64-linux-gnu.cmake`, `aarch64-linux-gnu.cmake`). Neither toolchain was installed, so neither was built. **NOT RUN.** |
 | Boards | `boards/*.yaml` | **Planned** | 84 descriptors, of which **71 are named `generic-*`**. A descriptor is not a port; none has been validated on hardware. |

hal/include/eos/hal_extended.h

@@ -77,7 +77,7 @@ void eos_pwm_deinit(uint8_t channel);
 int  eos_pwm_set_duty(uint8_t channel, uint16_t duty_pct_x10);
 int  eos_pwm_set_freq(uint8_t channel, uint32_t frequency_hz);
 int  eos_pwm_start(uint8_t channel);
-int  eos_pwm_stop(uint8_t channel);
+int  eos_pwm_stop(uint8_t channel);   /* idempotent: 0 if channel is initialized but not running */
 
 #endif /* EOS_ENABLE_PWM */
 

hal/src/hal_extended.c

@@ -13,7 +13,7 @@
 
 #if defined(EOS_MCU_STM32F4)
 
-#define REG32(addr) (*(volatile uint32_t *)(addr))
+#include "hal_stm32f4_regs.h"
 
 /* ================================================================
  * Flash — STM32F4 Internal Flash (FLASH_CR/SR at 0x40023C00)
@@ -207,7 +207,6 @@ int eos_wdt_set_callback(eos_wdt_callback_t cb, void *ctx) {
 #define RTC_CR    REG32(0x40002808U)
 #define RTC_ISR   REG32(0x4000280CU)
 #define RTC_WPR   REG32(0x40002824U)
-#define RCC_APB1ENR_REG REG32(0x40023840U)
 #define RCC_BDCR  REG32(0x40023870U)
 
 static uint8_t bcd_to_bin(uint8_t bcd) { return (bcd >> 4) * 10 + (bcd & 0xF); }

hal/src/hal_extended_stubs.c

@@ -89,42 +89,9 @@ int eos_dac_write_mv(uint8_t channel, uint32_t millivolts)
 
 /* ---- PWM ---- */
 #if EOS_ENABLE_PWM
-
-int eos_pwm_init(const eos_pwm_config_t *cfg)
-{
-    (void)cfg;
-    return -1;
-}
-
-void eos_pwm_deinit(uint8_t channel)
-{
-    (void)channel;
-}
-
-int eos_pwm_set_duty(uint8_t channel, uint16_t duty_pct_x10)
-{
-    (void)channel; (void)duty_pct_x10;
-    return -1;
-}
-
-int eos_pwm_set_freq(uint8_t channel, uint32_t frequency_hz)
-{
-    (void)channel; (void)frequency_hz;
-    return -1;
-}
-
-int eos_pwm_start(uint8_t channel)
-{
-    (void)channel;
-    return -1;
-}
-
-int eos_pwm_stop(uint8_t channel)
-{
-    (void)channel;
-    return -1;
-}
-
+/* PWM implementation moved to hal_pwm.c - platform-specific implementations
+ * for STM32F4 and Linux are provided there
+ */
 #endif /* EOS_ENABLE_PWM */
 
 /* ---- CAN ---- */