readahead: define config macro and osbdev func

For context, see issue #16 in the Reliance Edge repository on GitHub.
tuxera · Jan 12, 2021 · e66ade5 · e66ade5
1 parent 75b1efb
commit e66ade5
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diff --git a/include/redconfigchk.h b/include/redconfigchk.h
@@ -185,6 +185,15 @@
   #error "Configuration error: REDCONF_CHECKER must be defined."
 #endif
 
+/*  For the prototype, REDCONF_READAHEAD hasn't been added to all the redconf.h
+    files; assume it is disabled if undefined.
+*/
+#ifndef REDCONF_READAHEAD
+  #define REDCONF_READAHEAD 0
+#elif (REDCONF_READAHEAD != 0) && (REDCONF_READAHEAD != 1)
+  #error "Configuration error: REDCONF_READAHEAD must be either 0 or 1."
+#endif
+
 #if (REDCONF_READ_ONLY != 0) && (REDCONF_READ_ONLY != 1)
   #error "Configuration error: REDCONF_READ_ONLY must be either 0 or 1"
 #endif

diff --git a/include/redosserv.h b/include/redosserv.h
@@ -59,6 +59,9 @@ REDSTATUS RedOsBDevOpen(uint8_t bVolNum, BDEVOPENMODE mode);
 REDSTATUS RedOsBDevGetGeometry(uint8_t bVolNum, BDEVINFO *pInfo);
 REDSTATUS RedOsBDevClose(uint8_t bVolNum);
 REDSTATUS RedOsBDevRead(uint8_t bVolNum, uint64_t ullSectorStart, uint32_t ulSectorCount, void *pBuffer);
+#if REDCONF_READAHEAD == 1
+void RedOsBDevReadahead(uint8_t bVolNum, uint64_t ullSectorStart, uint32_t ulSectorCount);
+#endif
 
 #if REDCONF_READ_ONLY == 0
 REDSTATUS RedOsBDevWrite(uint8_t bVolNum, uint64_t ullSectorStart, uint32_t ulSectorCount, const void *pBuffer);

diff --git a/os/stub/services/osbdev.c b/os/stub/services/osbdev.c
@@ -192,6 +192,40 @@ REDSTATUS RedOsBDevRead(
 }
 
 
+#if REDCONF_READAHEAD == 1
+/** @brief Request asynchronous readahead of the specified sectors.
+
+    If the block device underlying @p bVolNum does not support readahead, or
+    would not benefit from it (think RAM disks), then this function can do
+    nothing and return.
+
+    This function cannot return an error since readahead is an optimization and
+    failures are not critical.
+
+    @param bVolNum          The volume number of the volume whose block device
+                            is being read from.
+    @param ullSectorStart   The starting sector number.
+    @param ulSectorCount    The number of sectors to readahead.
+*/
+void RedOsBDevReadahead(
+    uint8_t     bVolNum,
+    uint64_t    ullSectorStart,
+    uint32_t    ulSectorCount)
+{
+    if(    (bVolNum >= REDCONF_VOLUME_COUNT)
+        || !gaDisk[bVolNum].fOpen
+        || (gaDisk[bVolNum].mode == BDEV_O_WRONLY)
+        || !VOLUME_SECTOR_RANGE_IS_VALID(bVolNum, ullSectorStart, ulSectorCount))
+    {
+        REDERROR();
+    }
+    else
+    {
+    }
+}
+#endif /* REDCONF_READAHEAD == 1 */
+
+
 #if REDCONF_READ_ONLY == 0
 /** @brief Write sectors to a physical block device.