Changeset ed54cbf in mainline for uspace/drv/bus/isa/i8237.c

Timestamp:

2012-08-19T12:54:35Z (12 years ago)

Author:

Jan Vesely <jano.vesely@…>

Branches:

lfn, master, serial, ticket/834-toolchain-update, topic/msim-upgrade, topic/simplify-dev-export

Children:

b881226

Parents:

b28dabe

Message:

isa: Add and use helper functions. Add comments.

File:

• uspace/drv/bus/isa/i8237.c (modified) (8 diffs)

uspace/drv/bus/isa/i8237.c

@@ -273 +273 @@
 };
 
-/* Initialize I/O access to DMA controller I/O ports.
+/** Initialize I/O access to DMA controller I/O ports.
  *
  * @param controller DMA Controller structure to initialize.
  *
  * @return Error code.
- *
  */
 static inline int dma_controller_init(dma_controller_t *controller)
@@ -305 +304 @@
         
         return EOK;
+}
+
+/** Helper function. Channels 4,5,6, and 7 are 8 bit DMA.
+ * @pram channel DMA channel.
+ * @reutrn True, if channel is 4,5,6, or 7, false otherwise.
+ */
+static inline bool is_dma16(unsigned channel)
+{
+        return (channel >= 4) && (channel < 8);
+}
+
+/** Helper function. Channels 0,1,2, and 3 are 8 bit DMA.
+ * @pram channel DMA channel.
+ * @reutrn True, if channel is 0,1,2, or 3, false otherwise.
+ */
+static inline bool is_dma8(unsigned channel)
+{
+        return (channel < 4);
 }
 
@@ -325 +342 @@
     uint8_t mode)
 {
+        if (!is_dma8(channel) && !is_dma16(channel))
+                return ENOENT;
+
         if ((channel == 0) || (channel == 4))
                 return ENOTSUP;
-        
-        if (channel > 7)
-                return ENOENT;
         
         /* DMA is limited to 24bit addresses. */
@@ -336 +353 @@
         
         /* 8 bit channels use only 4 bits from the page register. */
-        if ((channel > 0) && (channel < 4) && (pa >= (1 << 20)))
+        if (is_dma8(channel) && (pa >= (1 << 20)))
                 return EINVAL;
 
@@ -353 +370 @@
         }
         
+        ddf_msg(LVL_DEBUG, "Unspoiled address: %p and size: %zu.", pa, size);
+        
         /* 16 bit transfers are a bit special */
-        ddf_msg(LVL_DEBUG, "Unspoiled address: %p and size: %zu.", pa, size);
-        if (channel > 4) {
+        if (is_dma16(channel)) {
                 /* Size must be aligned to 16 bits */
                 if ((size & 1) != 0) {
@@ -361 +379 @@
                         return EINVAL;
                 }
-                
+                /* Size is in 2byte words */
                 size >>= 1;
-                
                 /* Address is fun: lower 16 bits need to be shifted by 1 */
                 pa = ((pa & 0xffff) >> 1) | (pa & 0xff0000);
@@ -429 +446 @@
 }
 
-extern int dma_channel_remain(unsigned channel, uint16_t *size)
+/** Query remaining buffer size.
+ *
+ * @param channel DMA Channel 1, 2, 3 for 8 bit transfers,
+ *                    5, 6, 7 for 16 bit.
+ * @param size    Place to store number of bytes pending in the assigned buffer.
+ *
+ * @return Error code.
+ */
+int dma_channel_remain(unsigned channel, uint16_t *size)
 {
         assert(size);
+        if (!is_dma8(channel) && !is_dma16(channel))
+                return ENOENT;
+        
         if ((channel == 0) || (channel == 4))
                 return ENOTSUP;
-        
-        if (channel > 7)
-                return ENOENT;
         
         fibril_mutex_lock(&guard);
@@ -461 +486 @@
         const int remain = (value_high << 8 | value_low) + 1;
         /* 16 bit DMA size is in words */
-        *size =  channel >= 4 ? remain << 1 : remain;
+        *size =  is_dma16(channel) ? remain << 1 : remain;
         return EOK;
 }