tests/qtest: pca9555: test output-to-input reflection and pull-ups
Add tests covering the pin I/O semantics of the expander: output-driven pins reflected in the input register, the pull-up seen on input-configured pins, and the independence of the two 8-bit ports. Signed-off-by: Emmanuel Blot <emmanuel.blot@free.fr> Reviewed-by: Glenn Miles <milesg@linux.ibm.com> Link: https://lore.kernel.org/qemu-devel/20260709-catalina-upgrade-v1-11-82a63fead90c@free.fr Signed-off-by: Cédric Le Goater <clg@redhat.com>
Emmanuel Blot committed
Jul 9, 2026 at 17:23 UTC
0e964386792dcd40e6657155db8545a814eefa4b
1 file changed
+75
tests/qtest/pca9555-test.c
+75
@@ -28,6 +28,77 @@ static void test_reset_defaults(void *obj, void *data, QGuestAllocator *alloc)
28
g_assert_cmphex(i2c_get8(dev, PCA9535_CONFIG1), ==, 0xFF);
29
}
30
31
+/*
32
+ * When a pin is configured as output and driven low (output=0, config=0),
33
+ * the input register should reflect 0 for that pin.
34
+ * When driven high (output=1, config=0), input should reflect 1.
35
+ * When configured as input (config=1), PCA5555 pull-up makes it read 1.
36
+ */
37
+static void test_output_drives_input(void *obj, void *data,
38
+ QGuestAllocator *alloc)
39
+{
40
+ QI2CDevice *dev = (QI2CDevice *)obj;
41
+
42
+ i2c_set8(dev, PCA9535_CONFIG0, 0xF0);
43
+ i2c_set8(dev, PCA9535_OUTPUT0, 0xFA);
44
+
45
+ g_assert_cmphex(i2c_get8(dev, PCA9535_INPUT0), ==, 0xFA);
46
+
47
+ g_assert_cmphex(i2c_get8(dev, PCA9535_INPUT1), ==, 0xFF);
48
+
49
+ i2c_set8(dev, PCA9535_CONFIG0, 0x00);
50
+ i2c_set8(dev, PCA9535_OUTPUT0, 0x00);
51
+ g_assert_cmphex(i2c_get8(dev, PCA9535_INPUT0), ==, 0x00);
52
+
53
+ i2c_set8(dev, PCA9535_OUTPUT0, 0xFF);
54
+ g_assert_cmphex(i2c_get8(dev, PCA9535_INPUT0), ==, 0xFF);
55
+}
56
+
57
+/*
58
+ * When all pins are inputs (config=0xFF) and no external driver,
59
+ * PCA9555 pull-ups should make the input register read all ones.
60
+ * Switching a pin to output mode with output=0 should drive it low.
61
+ */
62
+static void test_input_pullup(void *obj, void *data, QGuestAllocator *alloc)
63
+{
64
+ QI2CDevice *dev = (QI2CDevice *)obj;
65
+
66
+ g_assert_cmphex(i2c_get8(dev, PCA9535_INPUT0), ==, 0xFF);
67
+ g_assert_cmphex(i2c_get8(dev, PCA9535_INPUT1), ==, 0xFF);
68
+
69
+ i2c_set8(dev, PCA9535_OUTPUT0, 0x00);
70
+ g_assert_cmphex(i2c_get8(dev, PCA9535_INPUT0), ==, 0xFF);
71
+
72
+ i2c_set8(dev, PCA9535_CONFIG0, 0x00);
73
+ g_assert_cmphex(i2c_get8(dev, PCA9535_INPUT0), ==, 0x00);
74
+}
75
+
76
+/*
77
+ * Test that both ports are independent: changing port 0 registers
78
+ * should not affect port 1 and vice versa.
79
+ */
80
+static void test_port_independence(void *obj, void *data,
81
+ QGuestAllocator *alloc)
82
+{
83
+ QI2CDevice *dev = (QI2CDevice *)obj;
84
+
85
+ i2c_set8(dev, PCA9535_CONFIG0, 0x00);
86
+ i2c_set8(dev, PCA9535_OUTPUT0, 0x00);
87
+
88
+ g_assert_cmphex(i2c_get8(dev, PCA9535_INPUT0), ==, 0x00);
89
+ g_assert_cmphex(i2c_get8(dev, PCA9535_INPUT1), ==, 0xFF);
90
+ g_assert_cmphex(i2c_get8(dev, PCA9535_CONFIG1), ==, 0xFF);
91
+ g_assert_cmphex(i2c_get8(dev, PCA9535_OUTPUT1), ==, 0xFF);
92
+
93
+ i2c_set8(dev, PCA9535_CONFIG1, 0x00);
94
+ i2c_set8(dev, PCA9535_OUTPUT1, 0xAA);
95
+
96
+ g_assert_cmphex(i2c_get8(dev, PCA9535_INPUT0), ==, 0x00);
97
+ g_assert_cmphex(i2c_get8(dev, PCA9535_INPUT1), ==, 0xAA);
98
+ g_assert_cmphex(i2c_get8(dev, PCA9535_OUTPUT0), ==, 0x00);
99
+ g_assert_cmphex(i2c_get8(dev, PCA9535_OUTPUT1), ==, 0xAA);
100
+}
101
+
102
static void pca9555_register_nodes(void)
103
{
104
QOSGraphEdgeOptions opts = {
@@ -39,6 +110,10 @@ static void pca9555_register_nodes(void)
110
qos_node_consumes("pca9555", "i2c-bus", &opts);
111
112
qos_add_test("reset-defaults", "pca9555", test_reset_defaults, NULL);
113
+ qos_add_test("output-drives-input", "pca9555", test_output_drives_input,
114
+ NULL);
115
+ qos_add_test("input-pullup", "pca9555", test_input_pullup, NULL);
116
+ qos_add_test("port-independence", "pca9555", test_port_independence, NULL);
117
}
118
119
libqos_init(pca9555_register_nodes);