HardwareTimer.cpp: save some space with an rcc_clk_id hack.

Since rcc_clk_ids for a peripheral now form a contiguous range by
peripheral number, we can infer the rcc_clk_id for a timer given its
number (e.g., can calculate RCC_TIMER2 given timerNum == 2). This lets
us use timer_foreach() to avoid keeping a table of available timers in
HardwareTimer.cpp.

The implementation is hackish, but can be fixed up later if need be.

Signed-off-by: Marti Bolivar <mbolivar@leaflabs.com>

1 files changed, 26 insertions, 97 deletions

diff --git a/wirish/HardwareTimer.cpp b/wirish/HardwareTimer.cpp
index ca8ea63..c35804c 100644
--- a/wirish/HardwareTimer.cpp
+++ b/wirish/HardwareTimer.cpp
@@ -25,7 +25,10 @@
  *****************************************************************************/
 
 #include <wirish/HardwareTimer.h>
-#include <wirish/boards.h>             // for CYCLES_PER_MICROSECOND
+
+#include <libmaple/rcc.h>          // for rcc_clk_id
+#include <wirish/boards.h>         // for CYCLES_PER_MICROSECOND
+#include <wirish/ext_interrupts.h> // for noInterrupts(), interrupts()
 #include <wirish/wirish_math.h>
 
 // TODO [0.1.0] Remove deprecated pieces
@@ -33,110 +36,36 @@
 #define MAX_RELOAD ((1 << 16) - 1)
 
 /*
- * Big ugly table of timers available on the MCU. Needed by the
- * HardwareTimer constructor. Sigh; maybe predefined instances weren't
- * such a bad idea. Oh well, at least the HardwareTimer interface is
- * officially unstable since v0.0.12; we can always get rid of this
- * later.
+ * Evil hack to infer this->dev from timerNum in the HardwareTimer
+ * constructor. See:
+ *
+ * http://www.parashift.com/c++-faq-lite/pointers-to-members.html#faq-33.2
+ * http://yosefk.com/c++fqa/function.html#fqa-33.2
  */
 
-#define MAX_NR_TIMERS 17 // No STM32 I've ever heard of has higher than TIMER17
-
-static timer_dev *devs[MAX_NR_TIMERS] = {
-#if STM32_HAVE_TIMER(1)
-    TIMER1,
-#else
-    NULL,
-#endif
-#if STM32_HAVE_TIMER(2)
-    TIMER2,
-#else
-    NULL,
-#endif
-#if STM32_HAVE_TIMER(3)
-    TIMER3,
-#else
-    NULL,
-#endif
-#if STM32_HAVE_TIMER(4)
-    TIMER4,
-#else
-    NULL,
-#endif
-#if STM32_HAVE_TIMER(5)
-    TIMER5,
-#else
-    NULL,
-#endif
-#if STM32_HAVE_TIMER(6)
-    TIMER6,
-#else
-    NULL,
-#endif
-#if STM32_HAVE_TIMER(7)
-    TIMER7,
-#else
-    NULL,
-#endif
-#if STM32_HAVE_TIMER(8)
-    TIMER8,
-#else
-    NULL,
-#endif
-#if STM32_HAVE_TIMER(9)
-    TIMER9,
-#else
-    NULL,
-#endif
-#if STM32_HAVE_TIMER(10)
-    TIMER10,
-#else
-    NULL,
-#endif
-#if STM32_HAVE_TIMER(11)
-    TIMER11,
-#else
-    NULL,
-#endif
-#if STM32_HAVE_TIMER(12)
-    TIMER12,
-#else
-    NULL,
-#endif
-#if STM32_HAVE_TIMER(13)
-    TIMER13,
-#else
-    NULL,
-#endif
-#if STM32_HAVE_TIMER(14)
-    TIMER14,
-#else
-    NULL,
-#endif
-#if STM32_HAVE_TIMER(15)
-    TIMER15,
-#else
-    NULL,
-#endif
-#if STM32_HAVE_TIMER(16)
-    TIMER16,
-#else
-    NULL,
-#endif
-#if STM32_HAVE_TIMER(17)
-    TIMER17,
-#else
-    NULL,
-#endif
-};
+extern "C" {
+    static timer_dev **this_devp;
+    static rcc_clk_id this_id;
+    static void set_this_dev(timer_dev *dev) {
+        if (dev->clk_id == this_id) {
+            *this_devp = dev;
+        }
+    }
+}
 
 /*
  * HardwareTimer routines
  */
 
 HardwareTimer::HardwareTimer(uint8 timerNum) {
-    ASSERT(timerNum <= MAX_NR_TIMERS);
-    this->dev = devs[timerNum - 1];
+    rcc_clk_id timerID = (rcc_clk_id)(RCC_TIMER1 + (timerNum - 1));
+    this->dev = NULL;
+    noInterrupts(); // Hack to ensure we're the only ones using
+                    // set_this_dev() and friends. TODO: use a lock.
+    this_id = timerID;
+    this_devp = &this->dev;
+    timer_foreach(set_this_dev);
+    interrupts();
     ASSERT(this->dev != NULL);
 }