[GitHub] [incubator-nuttx] davids5 commented on a diff in pull request #6834: modify iob to support header padding and alignment features

[GitBox <gi...@apache.org>]

davids5 commented on code in PR #6834:
URL: https://github.com/apache/incubator-nuttx/pull/6834#discussion_r944409428


##########
mm/iob/iob_initialize.c:
##########
@@ -30,14 +30,36 @@
 
 #include "iob.h"
 
+/****************************************************************************
+ * Pre-processor Definitions
+ ****************************************************************************/
+
+#define ROUNDUP(x, y)     (((x) + (y) - 1) / (y) * (y))
+
+/* Fix the I/O Buffer size with specified alignment size */
+
+#define IOB_ALIGN_SIZE    ROUNDUP(sizeof(struct iob_s), CONFIG_IOB_ALIGNMENT)
+#define IOB_BUFFER_SIZE   (IOB_ALIGN_SIZE * CONFIG_IOB_NBUFFERS + \
+                           CONFIG_IOB_ALIGNMENT - 1)
+
 /****************************************************************************
  * Private Data
  ****************************************************************************/
 
-/* This is a pool of pre-allocated I/O buffers */
+/* Following raw buffer will be divided into iob_s instances, the initial
+ * procedure will ensure that the member io_head of each iob_s is aligned
+ * to the CONFIG_IOB_ALIGNMENT memory boundary.
+ */
+
+static uint8_t g_iob_buffer[IOB_BUFFER_SIZE]
+#ifdef CONFIG_IOB_SECTION

Review Comment:
   Would you object to a #define IOB_LOCATION the is defined in Pre-processor Definitions 
   ```
   #ifdef CONFIG_IOB_SECTION
   #  define   IOB_LOCATION locate_data(CONFIG_IOB_SECTION)
   #else
   #  define   IOB_LOCATTION 
   #endif
   ```
   and used here?
   
   ```static uint8_t g_iob_buffer[IOB_BUFFER_SIZE] IOB_LOCATION;```
   
   
   



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