hw/net/xilinx_ethlite: Introduce txbuf_ptr() helper

For a particular physical address within the EthLite MMIO range,
addr_to_port_index() returns which port is accessed.

txbuf_ptr() points to the beginning of a (RAM) TX buffer
within the device state.

Signed-off-by: Philippe Mathieu-Daudé <philmd@linaro.org>
Reviewed-by: Edgar E. Iglesias <edgar.iglesias@amd.com>
Message-Id: <20241112181044.92193-10-philmd@linaro.org>

hw/net/xilinx_ethlite.c

@@ -27,6 +27,7 @@
 
 #include "qemu/osdep.h"
 #include "qemu/module.h"
+#include "qemu/bitops.h"
 #include "qom/object.h"
 #include "qapi/error.h"
 #include "exec/tswap.h"
@@ -87,6 +88,18 @@ static inline void eth_pulse_irq(XlnxXpsEthLite *s)
     }
 }
 
+static unsigned addr_to_port_index(hwaddr addr)
+{
+    return extract64(addr, 11, 1);
+}
+
+static void *txbuf_ptr(XlnxXpsEthLite *s, unsigned port_index)
+{
+    unsigned int rxbase = port_index * (0x800 / 4);
+
+    return &s->regs[rxbase + R_TX_BUF0];
+}
+
 static uint64_t
 eth_read(void *opaque, hwaddr addr, unsigned int size)
 {
@@ -119,6 +132,7 @@ eth_write(void *opaque, hwaddr addr,
           uint64_t val64, unsigned int size)
 {
     XlnxXpsEthLite *s = opaque;
+    unsigned int port_index = addr_to_port_index(addr);
     unsigned int base = 0;
     uint32_t value = val64;
 
@@ -132,12 +146,12 @@ eth_write(void *opaque, hwaddr addr,
 
             if ((value & (CTRL_P | CTRL_S)) == CTRL_S) {
                 qemu_send_packet(qemu_get_queue(s->nic),
-                                 (void *) &s->regs[base],
+                                 txbuf_ptr(s, port_index),
                                  s->regs[base + R_TX_LEN0]);
                 if (s->regs[base + R_TX_CTRL0] & CTRL_I)
                     eth_pulse_irq(s);
             } else if ((value & (CTRL_P | CTRL_S)) == (CTRL_P | CTRL_S)) {
-                memcpy(&s->conf.macaddr.a[0], &s->regs[base], 6);
+                memcpy(&s->conf.macaddr.a[0], txbuf_ptr(s, port_index), 6);
                 if (s->regs[base + R_TX_CTRL0] & CTRL_I)
                     eth_pulse_irq(s);
             }