Add a simple i2c peripheral to be used for testing I2C device
models. The peripheral has a fixed number of registers that can be
read and written.

Signed-off-by: Octavian Purdila <tavip@google.com>
---
 include/hw/misc/i2c_tester.h | 30 ++++++++++++
 hw/misc/i2c_tester.c         | 94 ++++++++++++++++++++++++++++++++++++
 hw/misc/Kconfig              |  5 ++
 hw/misc/meson.build          |  2 +
 4 files changed, 131 insertions(+)
 create mode 100644 include/hw/misc/i2c_tester.h
 create mode 100644 hw/misc/i2c_tester.c

diff --git a/include/hw/misc/i2c_tester.h b/include/hw/misc/i2c_tester.h
new file mode 100644
index 0000000000..f6b6491008
--- /dev/null
+++ b/include/hw/misc/i2c_tester.h
@@ -0,0 +1,30 @@
+/*
+ *
+ * Copyright (c) 2024 Google LLC
+ *
+ * SPDX-License-Identifier: GPL-2.0-or-later
+ *
+ * This work is licensed under the terms of the GNU GPL, version 2 or later.
+ * See the COPYING file in the top-level directory.
+ */
+
+#ifndef HW_I2C_TESTER_H
+#define HW_I2C_TESTER_H
+
+#include "qemu/osdep.h"
+#include "hw/i2c/i2c.h"
+#include "hw/irq.h"
+
+#define I2C_TESTER_NUM_REGS    0x31
+
+#define TYPE_I2C_TESTER "i2c-tester"
+#define I2C_TESTER(obj) OBJECT_CHECK(I2cTesterState, (obj), TYPE_I2C_TESTER)
+
+typedef struct {
+    I2CSlave i2c;
+    bool set_reg_idx;
+    uint8_t reg_idx;
+    uint8_t regs[I2C_TESTER_NUM_REGS];
+} I2cTesterState;
+
+#endif /* HW_I2C_TESTER_H */
diff --git a/hw/misc/i2c_tester.c b/hw/misc/i2c_tester.c
new file mode 100644
index 0000000000..3d7986a954
--- /dev/null
+++ b/hw/misc/i2c_tester.c
@@ -0,0 +1,94 @@
+/*
+ * Simple I2C peripheral for testing I2C device models.
+ *
+ * Copyright (c) 2024 Google LLC
+ *
+ * SPDX-License-Identifier: GPL-2.0-or-later
+ *
+ * This work is licensed under the terms of the GNU GPL, version 2 or later.
+ * See the COPYING file in the top-level directory.
+ */
+
+#include "hw/misc/i2c_tester.h"
+
+#include "qemu/log.h"
+#include "qemu/module.h"
+
+static void i2c_tester_reset(DeviceState *ds)
+{
+    I2cTesterState *s = I2C_TESTER(ds);
+
+    s->set_reg_idx = false;
+    s->reg_idx     = 0;
+    memset(s->regs, 0, I2C_TESTER_NUM_REGS);
+}
+
+static int i2c_tester_event(I2CSlave *i2c, enum i2c_event event)
+{
+    I2cTesterState *s = I2C_TESTER(i2c);
+
+    if (event == I2C_START_SEND) {
+        s->set_reg_idx = true;
+    }
+
+    return 0;
+}
+
+static uint8_t i2c_tester_rx(I2CSlave *i2c)
+{
+    I2cTesterState *s = I2C_TESTER(i2c);
+
+    if (s->reg_idx >= I2C_TESTER_NUM_REGS) {
+        qemu_log_mask(LOG_GUEST_ERROR, "%s: invalid reg 0x%02x\n", __func__,
+                      s->reg_idx);
+        return I2C_NACK;
+    }
+
+    return s->regs[s->reg_idx];
+}
+
+static int i2c_tester_tx(I2CSlave *i2c, uint8_t data)
+{
+    I2cTesterState *s = I2C_TESTER(i2c);
+
+    if (s->set_reg_idx) {
+        /* Setting the register in which the operation will be done. */
+        s->reg_idx = data;
+        s->set_reg_idx = false;
+        return 0;
+    }
+
+    if (s->reg_idx >= I2C_TESTER_NUM_REGS) {
+        qemu_log_mask(LOG_GUEST_ERROR, "%s: invalid reg 0x%02x\n", __func__,
+                      s->reg_idx);
+        return I2C_NACK;
+    }
+
+    /* Write reg data. */
+    s->regs[s->reg_idx] = data;
+
+    return 0;
+}
+
+static void i2c_tester_class_init(ObjectClass *oc, void *data)
+{
+    DeviceClass *dc = DEVICE_CLASS(oc);
+    I2CSlaveClass *isc = I2C_SLAVE_CLASS(oc);
+
+    dc->reset = i2c_tester_reset;
+
+    isc->event = i2c_tester_event;
+    isc->recv = i2c_tester_rx;
+    isc->send = i2c_tester_tx;
+}
+
+static const TypeInfo i2c_tester_types[] = {
+    {
+        .name = TYPE_I2C_TESTER,
+        .parent = TYPE_I2C_SLAVE,
+        .instance_size = sizeof(I2cTesterState),
+        .class_init = i2c_tester_class_init
+    },
+};
+
+DEFINE_TYPES(i2c_tester_types);
diff --git a/hw/misc/Kconfig b/hw/misc/Kconfig
index 4b688aead2..3e93c12c8e 100644
--- a/hw/misc/Kconfig
+++ b/hw/misc/Kconfig
@@ -213,6 +213,11 @@ config IOSB
 config XLNX_VERSAL_TRNG
     bool
 
+config I2C_TESTER
+    bool
+    default y if TEST_DEVICES
+    depends on I2C
+
 config FLEXCOMM
     bool
     select I2C
diff --git a/hw/misc/meson.build b/hw/misc/meson.build
index df36b45d9f..a0f7a52a23 100644
--- a/hw/misc/meson.build
+++ b/hw/misc/meson.build
@@ -157,6 +157,8 @@ system_ss.add(when: 'CONFIG_SBSA_REF', if_true: files('sbsa_ec.c'))
 # HPPA devices
 system_ss.add(when: 'CONFIG_LASI', if_true: files('lasi.c'))
 
+system_ss.add(when: 'CONFIG_I2C_TESTER', if_true: files('i2c_tester.c'))
+
 system_ss.add(when: 'CONFIG_FLEXCOMM', if_true: files('flexcomm.c'))
 system_ss.add(when: 'CONFIG_RT500_CLKCTL', if_true: files('rt500_clkctl0.c', 'rt500_clkctl1.c'))
 system_ss.add(when: 'CONFIG_RT500_RSTCTL', if_true: files('rt500_rstctl.c'))
-- 
2.46.0.295.g3b9ea8a38a-goog