Add PS/2 Model 50 emulation.

This commit also adds basic MCA emulation.
This commit also adds emulation of the PS/2 Type 1 DMA controller.

src/mca.c

@@ -0,0 +1,60 @@
+#include "ibm.h"
+#include "io.h"
+#include "mem.h"
+
+#include "mca.h"
+
+void    (*mca_card_write[8])(int addr, uint8_t val, void *priv);
+uint8_t  (*mca_card_read[8])(int addr, void *priv);
+void           *mca_priv[8];
+static int mca_index;
+static int mca_nr_cards;
+
+void mca_init(int nr_cards)
+{
+        int c;
+        
+        for (c = 0; c < 8; c++)
+                mca_card_read[c] = mca_card_write[c] = mca_priv[c] = NULL;
+        
+        mca_index = 0;
+        mca_nr_cards = nr_cards;
+}
+
+void mca_set_index(int index)
+{
+        mca_index = index;
+}
+
+uint8_t mca_read(uint16_t port)
+{
+        if (mca_index >= mca_nr_cards)
+                return 0xff;
+        if (!mca_card_read[mca_index])
+                return 0xff;
+        return mca_card_read[mca_index](port, mca_priv[mca_index]);
+}
+
+void mca_write(uint16_t port, uint8_t val)
+{
+        if (mca_index >= mca_nr_cards)
+                return;
+        if (mca_card_write[mca_index])
+                mca_card_write[mca_index](port, val, mca_priv[mca_index]);
+}
+
+void mca_add(uint8_t (*read)(int addr, void *priv), void (*write)(int addr, uint8_t val, void *priv), void *priv)
+{
+        int c;
+        
+        for (c = 0; c < mca_nr_cards; c++)
+        {
+                if (!mca_card_read[c] && !mca_card_write[c])
+                {
+                         mca_card_read[c] = read;
+                        mca_card_write[c] = write;
+                              mca_priv[c] = priv;
+                        return;
+                }
+        }
+}