GPT is usable without callbacks now (trigger, counter).

git-svn-id: svn://svn.code.sf.net/p/chibios/svn/branches/kernel_3_dev@6760 35acf78f-673a-0410-8e92-d51de3d6d3f4

os/hal/ports/STM32/LLD/TIMv1/gpt_lld.c

@@ -716,6 +716,7 @@ void gpt_lld_start_timer(GPTDriver *gptp, gptcnt_t interval) {
      SR bit 0 goes to 1. This is because the clearing of CNT has been inserted
      before the clearing of SR, to give it some time.*/
   gptp->tim->SR    = 0;                         /* Clear pending IRQs.      */
+  if (NULL != gptp->config->callback)
     gptp->tim->DIER |= STM32_TIM_DIER_UIE;      /* Update Event IRQ enabled.*/
   gptp->tim->CR1   = STM32_TIM_CR1_URS | STM32_TIM_CR1_CEN;
 }

os/hal/ports/STM32/LLD/TIMv1/gpt_lld.h

@@ -383,6 +383,8 @@ typedef struct {
   /**
    * @brief   Timer callback pointer.
    * @note    This callback is invoked on GPT counter events.
+   * @note    This callback can be set to @p NULL but in that case the
+   *          one-shot mode cannot be used.
    */
   gptcallback_t             callback;
   /* End of the mandatory fields.*/

os/hal/src/gpt.c

@@ -198,6 +198,7 @@ void gptStartOneShotI(GPTDriver *gptp, gptcnt_t interval) {
 
   osalDbgCheckClassI();
   osalDbgCheck(gptp != NULL);
+  osalDbgCheck(gptp->config->callback != NULL);
   osalDbgAssert(gptp->state == GPT_READY,
                 "invalid state");