Unaligned access trickery

c_common/Doxyfile

@@ -310,7 +310,7 @@ EXPAND_ONLY_PREDEF     = YES
 SEARCH_INCLUDES        = YES
 INCLUDE_PATH           =
 INCLUDE_FILE_PATTERNS  =
-PREDEFINED             = __attribute__(x)= PROFILER_ENABLED=YES INT_HANDLER=void UNUSED= ASSERT_WORD_SIZED(x)= DOXYGEN DOXYNAME(x)=x
+PREDEFINED             = __attribute__(x)= PROFILER_ENABLED=YES INT_HANDLER=void UNUSED= ASSERT_WORD_SIZED(x)= DOXYGEN DOXYNAME(x)=x __PACKED_STRUCT=
 EXPAND_AS_DEFINED      =
 SKIP_FUNCTION_MACROS   = YES
 

c_common/front_end_common_lib/include/buffered_eieio_defs.h

@@ -57,8 +57,11 @@ typedef enum buffered_operations {
     BUFFER_OPERATION_WRITE
 } buffered_operations;
 
-//! pointer to an EIEIO message
-typedef uint16_t* eieio_msg_t;
+//! Pointer to an EIEIO message
+typedef const uint16_t *eieio_msg_t;
+
+//! Pointer to a writable EIEIO message
+typedef uint16_t *eieio_writable_msg_t;
 
 //! The maximum sequence number
 #define MAX_SEQUENCE_NO 0xFF

c_common/front_end_common_lib/include/eieio.h

@@ -69,18 +69,27 @@ union eieio_header_bitfields {
         uint16_t count : 8;
         // Padding
         uint16_t : 2;
-        //! \brief The type of the packet (see eieio_data_message_types)
+        //! \brief The type of the packet (see ::eieio_data_message_types)
         uint16_t packet_type : 2;
         //! \brief Whether the payload is a timestamp
         uint16_t payload_is_timestamp : 1;
         //! \brief Whether to apply the current prefix to the payload
         uint16_t apply_payload_prefix : 1;
-        //! \brief Whether the prefix is applied to the upper or lower half of the
-        //! payload.
+        //! \brief Whether the prefix is applied to the upper or lower half of
+        //! the payload.
         uint16_t prefix_upper : 1;
         //! \brief Whether to apply the prefix
         uint16_t apply_prefix : 1;
     };
+    //! The bits in the packet type
+    struct {
+        uint16_t : 10;
+        //! Whether the packet has a payload.
+        uint16_t packet_has_payload : 1;
+        //! Whether the packet contains 32-bit values (or 16-bit if false).
+        uint16_t packet_is_32bit : 1;
+        uint16_t : 4;
+    };
     struct {
         //! \brief What command is encoded in the packet.
         uint16_t packet_command : 14;
@@ -99,7 +108,7 @@ typedef enum {
     //! Message is just a key, 32 bits long
     KEY_32_BIT,
     //! Message is a key and a payload, each 32 bits long
-    KEY_PAYLOAD_32_bIT
+    KEY_PAYLOAD_32_BIT
 } eieio_data_message_types;
 
 //! The EIEIO prefix types
@@ -108,4 +117,11 @@ typedef enum {
     PREFIX_TYPE_UPPER_HALF_WORD
 } eieio_prefix_types;
 
+//! Special packet classes
+enum {
+    //! \brief The packet is a command.
+    //! \details This is an illegal combination of bits for a data packet.
+    PACKET_CLASS_COMMAND = 1
+};
+
 #endif //INCLUDE_FEC_EIEIO_H

c_common/front_end_common_lib/include/recording.h

@@ -32,23 +32,22 @@
 typedef uint8_t channel_index_t;
 
 //! \brief records some data into a specific recording channel.
-//! \param[in] channel the channel to store the data into.
-//! \param[in] data the data to store into the channel.
-//! \param[in] size_bytes the number of bytes that this data will take up.
+//! \param[in] channel: the channel to store the data into.
+//! \param[in] data: the data to store into the channel.
+//! \param[in] size_bytes: the number of bytes that this data will take up.
 //!            This may be any number of bytes, not just whole words.
-//! \return boolean which is True if the data has been stored in the channel,
+//! \return True if the data has been stored in the channel,
 //!         False otherwise.
-bool recording_record(channel_index_t channel, void *data, size_t size_bytes);
+bool recording_record(channel_index_t channel, const void *data, size_t size_bytes);
 
-//! \brief Finishes recording - should only be called if recording_flags is
-//!        not 0
+//! \brief Finishes recording.
+//! \details should only be called if recording_flags is not 0
 void recording_finalise(void);
 
 //! \brief initialises the recording of data
-//! \param[in,out] recording_data_address The start of the data about the
-//!                                       recording, updated to point to just
-//!                                       after the data if return True.
-//!                                       Data is:
+//! \param[in,out] recording_data_address:
+//!     The start of the data about the recording, updated to point to just
+//!     after the data if return True. Data is:
 //! ```
 //! {
 //!    // number of potential recording regions

c_common/front_end_common_lib/src/recording.c

@@ -103,7 +103,7 @@ static inline void copy_data(
     }
 }
 
-bool recording_record(uint8_t channel, void *data, uint32_t size_bytes) {
+bool recording_record(uint8_t channel, const void *data, uint32_t size_bytes) {
     recording_channel_t *rec = &channels[channel];
     if (has_been_initialised(rec)) {
 
@@ -127,10 +127,9 @@ bool recording_record(uint8_t channel, void *data, uint32_t size_bytes) {
     return false;
 }
 
-__attribute__((noreturn)) void recording_bad_offset(
-  void *data, uint32_t size) {
-    log_error("DMA transfer of non-word data quantity in recording! "
-      "(data=0x%08x, size=0x%x)", data, size);
+NORETURN void recording_bad_offset(const void *data, uint32_t size) {
+    log_error("DMA transfer of non-word data quantity in recording! (data=0x%08x, size=0x%x)",
+            data, size);
     rt_error(RTE_SWERR);
 }
 
@@ -177,9 +176,7 @@ bool recording_initialize(
         *recording_flags = 0;
     }
 
-    /* Reserve the actual recording regions.
-     *
-     */
+    // Reserve the actual recording regions.
     for (uint32_t i = 0; i < n_regions; i++) {
         recording_region_t *region = &regions->regions[i];
         uint32_t space = region->space;

c_common/models/live_packet_gather/src/live_packet_gather.c

@@ -175,20 +175,18 @@ static struct lpg_config config;
 //!     _Only guaranteed to be half-word aligned._
 //! \param[in] index: Offset in count of _words_ into the buffer.
 //! \param[in] value: Value to write in (as little-endian).
-static inline void write_word(void *base, uint32_t index, uint32_t value) {
-    uint16_t *ary = base;
-    uint32_t idx = index * 2;
-    ary[idx++] = CLAMP16(value);
-    ary[idx] = CLAMP16(value >> 16);
+static inline void write_word(uint16_t *base, uint32_t index, uint32_t value) {
+    uint32_t *ary = __builtin_assume_aligned(base, 4, 2);
+    ary[index] = value;
 }
 
 //! \brief Simple mirror of write_word() for true 16 bit values.
 //! \param[in] base: place to write to
 //! \param[in] index: location in base to write to
 //! \param[in] value: the value to write to the base.
-static inline void write_short(void *base, uint32_t index, uint32_t value) {
-    uint16_t *ary = base;
-    ary[index] = CLAMP16(value);
+static inline void write_short(
+        uint16_t *base, uint32_t index, uint32_t value) {
+    base[index] = CLAMP16(value);
 }
 
 //! \brief Get how many events there are waiting to be sent