AMD/DC390 SCSI fixes of the day (August 4th, 2024)

Ported the latest changes/fixes to the above controller from QEMU and added a bios-less AMD Am53c974 device (non-DC390).
The latest changes fix the AMD-branded DOS ASPI drivers on both cards (even without bios).

src/fifo8.c

@@ -21,14 +21,19 @@
 #include <86box/86box.h>
 #include <86box/fifo8.h>
 
+void
+fifo8_reset(Fifo8 *fifo)
+{
+    fifo->num  = 0;
+    fifo->head = 0;
+}
+
 void
 fifo8_create(Fifo8 *fifo, uint32_t capacity)
 {
-    fifo->data = (uint8_t *) malloc(capacity);
-    memset(fifo->data, 0, capacity);
+    fifo->data = (uint8_t *) calloc(1, capacity);
     fifo->capacity = capacity;
-    fifo->head     = 0;
-    fifo->num      = 0;
+    fifo8_reset(fifo);
 }
 
 void
@@ -54,7 +59,7 @@ fifo8_push_all(Fifo8 *fifo, const uint8_t *data, uint32_t num)
     uint32_t start;
     uint32_t avail;
 
-    assert(fifo->num + num <= fifo->capacity);
+    assert((fifo->num + num) <= fifo->capacity);
 
     start = (fifo->head + fifo->num) % fifo->capacity;
 
@@ -81,25 +86,72 @@ fifo8_pop(Fifo8 *fifo)
     return ret;
 }
 
-const uint8_t *
-fifo8_pop_buf(Fifo8 *fifo, uint32_t max, uint32_t *num)
+static const uint8_t
+*fifo8_peekpop_buf(Fifo8 *fifo, uint32_t max, uint32_t *numptr, int do_pop)
 {
-    const uint8_t *ret;
+    uint8_t *ret;
+    uint32_t num;
+
+    assert((max > 0) && (max <= fifo->num));
+    num = MIN(fifo->capacity - fifo->head, max);
+    ret = &fifo->data[fifo->head];
+
+    if (do_pop) {
+        fifo->head += num;
+        fifo->head %= fifo->capacity;
+        fifo->num -= num;
+    }
+    if (numptr)
+        *numptr = num;
 
-    assert(max > 0 && max <= fifo->num);
-    *num = MIN(fifo->capacity - fifo->head, max);
-    ret  = &fifo->data[fifo->head];
-    fifo->head += *num;
-    fifo->head %= fifo->capacity;
-    fifo->num -= *num;
     return ret;
 }
 
-void
-fifo8_reset(Fifo8 *fifo)
+const uint8_t
+*fifo8_peek_bufptr(Fifo8 *fifo, uint32_t max, uint32_t *numptr)
 {
-    fifo->num  = 0;
-    fifo->head = 0;
+    return fifo8_peekpop_buf(fifo, max, numptr, 0);
+}
+
+const uint8_t
+*fifo8_pop_bufptr(Fifo8 *fifo, uint32_t max, uint32_t *numptr)
+{
+    return fifo8_peekpop_buf(fifo, max, numptr, 1);
+}
+
+uint32_t
+fifo8_pop_buf(Fifo8 *fifo, uint8_t *dest, uint32_t destlen)
+{
+    const uint8_t *buf;
+    uint32_t n1, n2 = 0;
+    uint32_t len;
+
+    if (destlen == 0)
+        return 0;
+
+    len = destlen;
+    buf = fifo8_pop_bufptr(fifo, len, &n1);
+    if (dest)
+        memcpy(dest, buf, n1);
+
+    /* Add FIFO wraparound if needed */
+    len -= n1;
+    len = MIN(len, fifo8_num_used(fifo));
+    if (len) {
+        buf = fifo8_pop_bufptr(fifo, len, &n2);
+        if (dest) {
+            memcpy(&dest[n1], buf, n2);
+        }
+    }
+
+    return n1 + n2;
+}
+
+void
+fifo8_drop(Fifo8 *fifo, uint32_t len)
+{
+    len -= fifo8_pop_buf(fifo, NULL, len);
+    assert(len == 0);
 }
 
 int

src/include/86box/fifo8.h

@@ -69,28 +69,80 @@ extern uint8_t fifo8_pop(Fifo8 *fifo);
 /**
  * fifo8_pop_buf:
  * @fifo: FIFO to pop from
- * @max: maximum number of bytes to pop
- * @num: actual number of returned bytes
+ * @dest: the buffer to write the data into (can be NULL)
+ * @destlen: size of @dest and maximum number of bytes to pop
  *
- * Pop a number of elements from the FIFO up to a maximum of max. The buffer
+ * Pop a number of elements from the FIFO up to a maximum of @destlen.
+ * The popped data is copied into the @dest buffer.
+ * Care is taken when the data wraps around in the ring buffer.
+ *
+ * Returns: number of bytes popped.
+ */
+extern uint32_t fifo8_pop_buf(Fifo8 *fifo, uint8_t *dest, uint32_t destlen);
+
+/**
+ * fifo8_pop_bufptr:
+ * @fifo: FIFO to pop from
+ * @max: maximum number of bytes to pop
+ * @numptr: pointer filled with number of bytes returned (can be NULL)
+ *
+ * New code should prefer to use fifo8_pop_buf() instead of fifo8_pop_bufptr().
+ *
+ * Pop a number of elements from the FIFO up to a maximum of @max. The buffer
  * containing the popped data is returned. This buffer points directly into
- * the FIFO backing store and data is invalidated once any of the fifo8_* APIs
- * are called on the FIFO.
+ * the internal FIFO backing store and data (without checking for overflow!)
+ * and is invalidated once any of the fifo8_* APIs are called on the FIFO.
  *
  * The function may return fewer bytes than requested when the data wraps
  * around in the ring buffer; in this case only a contiguous part of the data
  * is returned.
  *
- * The number of valid bytes returned is populated in *num; will always return
- * at least 1 byte. max must not be 0 or greater than the number of bytes in
- * the FIFO.
+ * The number of valid bytes returned is populated in *@numptr; will always
+ * return at least 1 byte. max must not be 0 or greater than the number of
+ * bytes in the FIFO.
  *
  * Clients are responsible for checking the availability of requested data
  * using fifo8_num_used().
  *
  * Returns: A pointer to popped data.
  */
-extern const uint8_t *fifo8_pop_buf(Fifo8 *fifo, uint32_t max, uint32_t *num);
+extern const uint8_t *fifo8_pop_bufptr(Fifo8 *fifo, uint32_t max, uint32_t *numptr);
+
+/**
+ * fifo8_peek_bufptr: read upto max bytes from the fifo
+ * @fifo: FIFO to read from
+ * @max: maximum number of bytes to peek
+ * @numptr: pointer filled with number of bytes returned (can be NULL)
+ *
+ * Peek into a number of elements from the FIFO up to a maximum of @max.
+ * The buffer containing the data peeked into is returned. This buffer points
+ * directly into the FIFO backing store. Since data is invalidated once any
+ * of the fifo8_* APIs are called on the FIFO, it is the caller responsibility
+ * to access it before doing further API calls.
+ *
+ * The function may return fewer bytes than requested when the data wraps
+ * around in the ring buffer; in this case only a contiguous part of the data
+ * is returned.
+ *
+ * The number of valid bytes returned is populated in *@numptr; will always
+ * return at least 1 byte. max must not be 0 or greater than the number of
+ * bytes in the FIFO.
+ *
+ * Clients are responsible for checking the availability of requested data
+ * using fifo8_num_used().
+ *
+ * Returns: A pointer to peekable data.
+ */
+extern const uint8_t *fifo8_peek_bufptr(Fifo8 *fifo, uint32_t max, uint32_t *numptr);
+
+/**
+ * fifo8_drop:
+ * @fifo: FIFO to drop bytes
+ * @len: number of bytes to drop
+ *
+ * Drop (consume) bytes from a FIFO.
+ */
+extern void fifo8_drop(Fifo8 *fifo, uint32_t len);
 
 /**
  * fifo8_reset:

src/include/86box/scsi_pcscsi.h

@@ -25,6 +25,7 @@
 #ifndef SCSI_PCSCSI_H
 #define SCSI_PCSCSI_H
 
+extern const device_t am53c974_pci_device;
 extern const device_t dc390_pci_device;
 extern const device_t ncr53c90a_mca_device;
 

src/scsi/scsi.c

@@ -82,6 +82,7 @@ static SCSI_CARD scsi_cards[] = {
     { &ncr53c825a_pci_device,    },
     { &ncr53c860_pci_device,     },
     { &ncr53c875_pci_device,     },
+    { &am53c974_pci_device,      },
     { &dc390_pci_device,         },
     { &buslogic_445s_device,     },
     { &buslogic_445c_device,     },