[Qemu-devel] [PATCH for-2.1 v2 2/2] util/fifo: Generalise for common integer widths

[Peter Crosthwaite]

Add support for 16, 32 and 64 bit width FIFOs. The push and pop
functions are patched to accept uint64_t always to support up to 64bit
integer elements. The element width is set at creation time.

The backing storage for all element types is still uint8_t regardless of
element width so some save-load logic is needed to handle endianness
issue WRT VMSD.

Signed-off-by: Peter Crosthwaite <address@hidden>
---

 hw/char/serial.c        |   4 +-
 hw/net/allwinner_emac.c |   6 +--
 hw/ssi/xilinx_spi.c     |   4 +-
 hw/ssi/xilinx_spips.c   |   4 +-
 include/qemu/fifo.h     |  19 +++++----
 util/fifo.c             | 109 +++++++++++++++++++++++++++++++++++++++++-------
 6 files changed, 114 insertions(+), 32 deletions(-)

diff --git a/hw/char/serial.c b/hw/char/serial.c
index a0d8024..3060769 100644
--- a/hw/char/serial.c
+++ b/hw/char/serial.c
@@ -659,8 +659,8 @@ void serial_realize_core(SerialState *s, Error **errp)
 
     qemu_chr_add_handlers(s->chr, serial_can_receive1, serial_receive1,
                           serial_event, s);
-    fifo_create(&s->recv_fifo, UART_FIFO_LENGTH);
-    fifo_create(&s->xmit_fifo, UART_FIFO_LENGTH);
+    fifo_create(&s->recv_fifo, UART_FIFO_LENGTH, 8);
+    fifo_create(&s->xmit_fifo, UART_FIFO_LENGTH, 8);
 }
 
 void serial_exit_core(SerialState *s)
diff --git a/hw/net/allwinner_emac.c b/hw/net/allwinner_emac.c
index e804411..2a0d2ac 100644
--- a/hw/net/allwinner_emac.c
+++ b/hw/net/allwinner_emac.c
@@ -455,9 +455,9 @@ static void aw_emac_realize(DeviceState *dev, Error **errp)
                           object_get_typename(OBJECT(dev)), dev->id, s);
     qemu_format_nic_info_str(qemu_get_queue(s->nic), s->conf.macaddr.a);
 
-    fifo_create(&s->rx_fifo, RX_FIFO_SIZE);
-    fifo_create(&s->tx_fifo[0], TX_FIFO_SIZE);
-    fifo_create(&s->tx_fifo[1], TX_FIFO_SIZE);
+    fifo_create(&s->rx_fifo, RX_FIFO_SIZE, 8);
+    fifo_create(&s->tx_fifo[0], TX_FIFO_SIZE, 8);
+    fifo_create(&s->tx_fifo[1], TX_FIFO_SIZE, 8);
 }
 
 static Property aw_emac_properties[] = {
diff --git a/hw/ssi/xilinx_spi.c b/hw/ssi/xilinx_spi.c
index 8fe3072..cac666b 100644
--- a/hw/ssi/xilinx_spi.c
+++ b/hw/ssi/xilinx_spi.c
@@ -341,8 +341,8 @@ static int xilinx_spi_init(SysBusDevice *sbd)
 
     s->irqline = -1;
 
-    fifo_create(&s->tx_fifo, FIFO_CAPACITY);
-    fifo_create(&s->rx_fifo, FIFO_CAPACITY);
+    fifo_create(&s->tx_fifo, FIFO_CAPACITY, 8);
+    fifo_create(&s->rx_fifo, FIFO_CAPACITY, 8);
 
     return 0;
 }
diff --git a/hw/ssi/xilinx_spips.c b/hw/ssi/xilinx_spips.c
index d7d4c41..a7a639f 100644
--- a/hw/ssi/xilinx_spips.c
+++ b/hw/ssi/xilinx_spips.c
@@ -669,8 +669,8 @@ static void xilinx_spips_realize(DeviceState *dev, Error 
**errp)
 
     s->irqline = -1;
 
-    fifo_create(&s->rx_fifo, xsc->rx_fifo_size);
-    fifo_create(&s->tx_fifo, xsc->tx_fifo_size);
+    fifo_create(&s->rx_fifo, xsc->rx_fifo_size, 8);
+    fifo_create(&s->tx_fifo, xsc->tx_fifo_size, 8);
 }
 
 static void xilinx_qspips_realize(DeviceState *dev, Error **errp)
diff --git a/include/qemu/fifo.h b/include/qemu/fifo.h
index 44766b3..8738027 100644
--- a/include/qemu/fifo.h
+++ b/include/qemu/fifo.h
@@ -5,8 +5,12 @@
 
 typedef struct {
     /* All fields are private */
+    int width; /* byte width each each element */
+    uint32_t capacity; /* number of elements */
+
     uint8_t *data;
-    uint32_t capacity;
+    uint32_t buffer_size;
+
     uint32_t head;
     uint32_t num;
 } Fifo;
@@ -14,13 +18,14 @@ typedef struct {
 /**
  * fifo_create:
  * @fifo: struct Fifo to initialise with new FIFO
- * @capacity: capacity of the newly created FIFO
+ * @capacity: capacity (number of elements) of the newly created FIFO
+ * @width: integer width of each element. Must be 8, 16, 32 or 64.
  *
  * Create a FIFO of the specified size. Clients should call fifo_destroy()
  * when finished using the fifo. The FIFO is initially empty.
  */
 
-void fifo_create(Fifo *fifo, uint32_t capacity);
+void fifo_create(Fifo *fifo, uint32_t capacity, int width);
 
 /**
  * fifo_destroy:
@@ -41,7 +46,7 @@ void fifo_destroy(Fifo *fifo);
  * Clients are responsible for checking for fullness using fifo_is_full().
  */
 
-void fifo_push(Fifo *fifo, uint8_t data);
+void fifo_push(Fifo *fifo, uint64_t data);
 
 /**
  * fifo_push_all:
@@ -54,7 +59,7 @@ void fifo_push(Fifo *fifo, uint8_t data);
  * fifo_num_free().
  */
 
-void fifo_push_all(Fifo *fifo, const uint8_t *data, uint32_t num);
+void fifo_push_all(Fifo *fifo, const void *data, uint32_t num);
 
 /**
  * fifo_pop:
@@ -66,7 +71,7 @@ void fifo_push_all(Fifo *fifo, const uint8_t *data, uint32_t 
num);
  * Returns: The popped data value.
  */
 
-uint8_t fifo_pop(Fifo *fifo);
+uint64_t fifo_pop(Fifo *fifo);
 
 /**
  * fifo_pop_buf:
@@ -93,7 +98,7 @@ uint8_t fifo_pop(Fifo *fifo);
  * Returns: A pointer to popped data.
  */
 
-const uint8_t *fifo_pop_buf(Fifo *fifo, uint32_t max, uint32_t *num);
+const void *fifo_pop_buf(Fifo *fifo, uint32_t max, uint32_t *num);
 
 /**
  * fifo_reset:
diff --git a/util/fifo.c b/util/fifo.c
index ffadf55..51318ad 100644
--- a/util/fifo.c
+++ b/util/fifo.c
@@ -15,9 +15,11 @@
 #include "qemu-common.h"
 #include "qemu/fifo.h"
 
-void fifo_create(Fifo *fifo, uint32_t capacity)
+void fifo_create(Fifo *fifo, uint32_t capacity, int width)
 {
-    fifo->data = g_new(uint8_t, capacity);
+    assert(width == 8 || width == 16 || width == 32 || width == 64);
+    fifo->width = width / 8;
+    fifo->data = g_new(uint8_t, capacity * fifo->width);
     fifo->capacity = capacity;
     fifo->head = 0;
     fifo->num = 0;
@@ -28,16 +30,33 @@ void fifo_destroy(Fifo *fifo)
     g_free(fifo->data);
 }
 
-void fifo_push(Fifo *fifo, uint8_t data)
+void fifo_push(Fifo *fifo, uint64_t data)
 {
+    uint32_t next_idx = (fifo->head + fifo->num) % fifo->capacity;
+
     if (fifo->num == fifo->capacity) {
         abort();
     }
-    fifo->data[(fifo->head + fifo->num) % fifo->capacity] = data;
+    switch (fifo->width) {
+    case(1):
+        ((uint8_t *)fifo->data)[next_idx] = data;
+        break;
+    case(2):
+        ((uint16_t *)fifo->data)[next_idx] = data;
+        break;
+    case(4):
+        ((uint32_t *)fifo->data)[next_idx] = data;
+        break;
+    case(8):
+        ((uint64_t *)fifo->data)[next_idx] = data;
+        break;
+    default:
+        abort();
+    }
     fifo->num++;
 }
 
-void fifo_push_all(Fifo *fifo, const uint8_t *data, uint32_t num)
+void fifo_push_all(Fifo *fifo, const void *data, uint32_t num)
 {
     uint32_t start, avail;
 
@@ -48,38 +67,51 @@ void fifo_push_all(Fifo *fifo, const uint8_t *data, 
uint32_t num)
     start = (fifo->head + fifo->num) % fifo->capacity;
 
     if (start + num <= fifo->capacity) {
-        memcpy(&fifo->data[start], data, num);
+        memcpy(&fifo->data[start * fifo->width], data, num * fifo->width);
     } else {
         avail = fifo->capacity - start;
-        memcpy(&fifo->data[start], data, avail);
-        memcpy(&fifo->data[0], &data[avail], num - avail);
+        memcpy(&fifo->data[start * fifo->width], data, avail * fifo->width);
+        memcpy(&fifo->data[0], data + avail * fifo->width,
+               (num - avail) * fifo->width);
     }
 
     fifo->num += num;
 }
 
-uint8_t fifo_pop(Fifo *fifo)
+uint64_t fifo_pop(Fifo *fifo)
 {
-    uint8_t ret;
+    uint32_t next_idx;
 
     if (fifo->num == 0) {
         abort();
     }
-    ret = fifo->data[fifo->head++];
+    next_idx = fifo->head++;
     fifo->head %= fifo->capacity;
     fifo->num--;
-    return ret;
+    switch (fifo->width) {
+    case(1):
+        return ((uint8_t *)fifo->data)[next_idx];
+    case(2):
+        return ((uint16_t *)fifo->data)[next_idx];
+    case(4):
+        return ((uint32_t *)fifo->data)[next_idx];
+    case(8):
+        return ((uint64_t *)fifo->data)[next_idx];
+    default:
+        abort();
+        return 0; /* unreachable */
+    }
 }
 
-const uint8_t *fifo_pop_buf(Fifo *fifo, uint32_t max, uint32_t *num)
+const void *fifo_pop_buf(Fifo *fifo, uint32_t max, uint32_t *num)
 {
-    uint8_t *ret;
+    void *ret;
 
     if (max == 0 || max > fifo->num) {
         abort();
     }
     *num = MIN(fifo->capacity - fifo->head, max);
-    ret = &fifo->data[fifo->head];
+    ret = &fifo->data[fifo->head * fifo->width];
     fifo->head += *num;
     fifo->head %= fifo->capacity;
     fifo->num -= *num;
@@ -112,13 +144,58 @@ uint32_t fifo_num_used(Fifo *fifo)
     return fifo->num;
 }
 
+/* Always store buffer data in little (arbitrarily chosen) endian format to
+ * allow for migration to/from BE <-> LE hosts.
+ */
+
+static inline void fifo_save_load_swap(Fifo *fifo)
+{
+#ifdef HOST_WORDS_BIGENDIAN
+    int i;
+    uint16_t *d16 = (uint16_t *)fifo->data;
+    uint32_t *d32 = (uint32_t *)fifo->data;
+    uint64_t *d64 = (uint64_t *)fifo->data;
+
+    for (i = 0; i < fifo->capacity; ++i) {
+        switch (fifo->width) {
+        case(1):
+            return;
+        case(2):
+            d16[i] = bswap16(d16[i]);
+            break;
+        case(4):
+            d32[i] = bswap32(d32[i]);
+            break;
+        case(8):
+            d64[i] = bswap64(d64[i]);
+            break;
+        default:
+            abort();
+        }
+    }
+#endif
+}
+
+static void fifo_pre_save(void *opaque)
+{
+    fifo_save_load_swap((Fifo *)opaque);
+}
+
+static int fifo_post_load(void *opaque, int version_id)
+{
+    fifo_save_load_swap((Fifo *)opaque);
+    return 0;
+}
+
 const VMStateDescription vmstate_fifo = {
     .name = "Fifo8",
     .version_id = 1,
     .minimum_version_id = 1,
     .minimum_version_id_old = 1,
+    .pre_save = fifo_pre_save,
+    .post_load = fifo_post_load,
     .fields      = (VMStateField[]) {
-        VMSTATE_VBUFFER_UINT32(data, Fifo, 1, NULL, 0, capacity),
+        VMSTATE_VBUFFER_UINT32(data, Fifo, 1, NULL, 0, buffer_size),
         VMSTATE_UINT32(head, Fifo),
         VMSTATE_UINT32(num, Fifo),
         VMSTATE_END_OF_LIST()
-- 
1.9.1.1.gbb9f595