[PULL 48/83] hw/gpio: pca9554: add PCA9536 support

From: Emmanuel Blot <[email protected]>

The PCA9536 is a 4-bit I/O expander that's register-compatible with the
PCA9554 but only has 4 pins.  Rather than duplicating the whole driver,
make the existing PCA9554 model parameterizable and register PCA9536 as
a subtype.

Introduce a PCA9554Class with a pin_count property, and replace every
hard-coded PCA9554_PIN_COUNT reference in the driver with the class
value.  The reset function now computes the correct pin mask from
pin_count instead of assuming 0xFF.

Signed-off-by: Emmanuel Blot <[email protected]>
Reviewed-by: Glenn Miles <[email protected]>
Link: https://lore.kernel.org/qemu-devel/[email protected]
Signed-off-by: Cédric Le Goater <[email protected]>
---
 include/hw/gpio/pca9554.h |  2 +
 hw/gpio/pca9554.c         | 79 ++++++++++++++++++++++++++-------------
 2 files changed, 54 insertions(+), 27 deletions(-)

diff --git a/include/hw/gpio/pca9554.h b/include/hw/gpio/pca9554.h
index 54bfc4c4c7a0..c09108e8b650 100644
--- a/include/hw/gpio/pca9554.h
+++ b/include/hw/gpio/pca9554.h
@@ -12,12 +12,14 @@
 #include "qom/object.h"
 
 #define TYPE_PCA9554 "pca9554"
+#define TYPE_PCA9536 "pca9536"
 typedef struct PCA9554State PCA9554State;
 DECLARE_INSTANCE_CHECKER(PCA9554State, PCA9554,
                          TYPE_PCA9554)
 
 #define PCA9554_NR_REGS 4
 #define PCA9554_PIN_COUNT 8
+#define PCA9536_PIN_COUNT 4
 
 struct PCA9554State {
     /*< private >*/
diff --git a/hw/gpio/pca9554.c b/hw/gpio/pca9554.c
index 8427e01e9b23..b44ec0d9991c 100644
--- a/hw/gpio/pca9554.c
+++ b/hw/gpio/pca9554.c
@@ -24,6 +24,8 @@ struct PCA9554Class {
     /*< private >*/
     I2CSlaveClass parent_class;
     /*< public >*/
+
+    uint8_t pin_count;
 };
 typedef struct PCA9554Class PCA9554Class;
 
@@ -37,12 +39,13 @@ static const char *pin_state[] = {"low", "high"};
 
 static void pca9554_update_pin_input(PCA9554State *s)
 {
+    PCA9554Class *pc = PCA9554_GET_CLASS(s);
     int i;
     uint8_t config = s->regs[PCA9554_CONFIG];
     uint8_t output = s->regs[PCA9554_OUTPUT];
     uint8_t internal_state = config | output;
 
-    for (i = 0; i < PCA9554_PIN_COUNT; i++) {
+    for (i = 0; i < pc->pin_count; i++) {
         uint8_t bit_mask = 1 << i;
         uint8_t internal_pin_state = (internal_state >> i) & 0x1;
         uint8_t old_value = s->regs[PCA9554_INPUT] & bit_mask;
@@ -67,7 +70,7 @@ static void pca9554_update_pin_input(PCA9554State *s)
             break;
         }
 
-        /* update irq state only if pin state changed */
+        /* drive the per-pin GPIO output only if the pin level changed */
         new_value = s->regs[PCA9554_INPUT] & bit_mask;
         if (new_value != old_value) {
             if (new_value) {
@@ -99,6 +102,12 @@ static uint8_t pca9554_read(PCA9554State *s, uint8_t reg)
 
 static void pca9554_write(PCA9554State *s, uint8_t reg, uint8_t data)
 {
+    PCA9554Class *pc = PCA9554_GET_CLASS(s);
+    uint8_t pin_mask = (1 << pc->pin_count) - 1;
+
+    /* Variants narrower than 8 bits ignore the unimplemented upper pins. */
+    data &= pin_mask;
+
     switch (reg) {
     case PCA9554_OUTPUT:
     case PCA9554_CONFIG:
@@ -157,7 +166,7 @@ static void pca9554_get_pin(Object *obj, Visitor *v, const char *name,
         error_setg(errp, "%s: error reading %s", __func__, name);
         return;
     }
-    if (pin < 0 || pin >= PCA9554_PIN_COUNT) {
+    if (pin < 0 || pin >= PCA9554_GET_CLASS(s)->pin_count) {
         error_setg(errp, "%s invalid pin %s", __func__, name);
         return;
     }
@@ -184,7 +193,7 @@ static void pca9554_set_pin(Object *obj, Visitor *v, const char *name,
         error_setg(errp, "%s: error reading %s", __func__, name);
         return;
     }
-    if (pin < 0 || pin >= PCA9554_PIN_COUNT) {
+    if (pin < 0 || pin >= PCA9554_GET_CLASS(s)->pin_count) {
         error_setg(errp, "%s invalid pin %s", __func__, name);
         return;
     }
@@ -232,13 +241,15 @@ static const VMStateDescription pca9554_vmstate = {
 static void pca9554_reset(DeviceState *dev)
 {
     PCA9554State *s = PCA9554(dev);
+    PCA9554Class *pc = PCA9554_GET_CLASS(s);
+    uint8_t pin_mask = (1 << pc->pin_count) - 1;
 
-    s->regs[PCA9554_INPUT] = 0xFF;
-    s->regs[PCA9554_OUTPUT] = 0xFF;
+    s->regs[PCA9554_INPUT] = pin_mask;
+    s->regs[PCA9554_OUTPUT] = pin_mask;
     s->regs[PCA9554_POLARITY] = 0x0; /* No pins are inverted */
-    s->regs[PCA9554_CONFIG] = 0xFF; /* All pins are inputs */
+    s->regs[PCA9554_CONFIG] = pin_mask; /* All pins are inputs */
 
-    memset(s->ext_state, PCA9554_PIN_HIZ, PCA9554_PIN_COUNT);
+    memset(s->ext_state, PCA9554_PIN_HIZ, pc->pin_count);
     pca9554_update_pin_input(s);
 
     s->pointer = 0x0;
@@ -247,9 +258,10 @@ static void pca9554_reset(DeviceState *dev)
 
 static void pca9554_initfn(Object *obj)
 {
+    PCA9554Class *pc = PCA9554_GET_CLASS(obj);
     int pin;
 
-    for (pin = 0; pin < PCA9554_PIN_COUNT; pin++) {
+    for (pin = 0; pin < pc->pin_count; pin++) {
         char *name;
 
         name = g_strdup_printf("pin%d", pin);
@@ -269,23 +281,24 @@ static void pca9554_set_ext_state(PCA9554State *s, int pin, int level)
 
 static void pca9554_gpio_in_handler(void *opaque, int pin, int level)
 {
-
     PCA9554State *s = PCA9554(opaque);
+    PCA9554Class *pc = PCA9554_GET_CLASS(s);
 
-    assert((pin >= 0) && (pin < PCA9554_PIN_COUNT));
+    assert((pin >= 0) && (pin < pc->pin_count));
     pca9554_set_ext_state(s, pin, level);
 }
 
 static void pca9554_realize(DeviceState *dev, Error **errp)
 {
     PCA9554State *s = PCA9554(dev);
+    PCA9554Class *pc = PCA9554_GET_CLASS(s);
 
     if (!s->description) {
-        s->description = g_strdup("pca9554");
+        s->description = g_strdup(object_get_typename(OBJECT(dev)));
     }
 
-    qdev_init_gpio_out(dev, s->gpio_out, PCA9554_PIN_COUNT);
-    qdev_init_gpio_in(dev, pca9554_gpio_in_handler, PCA9554_PIN_COUNT);
+    qdev_init_gpio_out(dev, s->gpio_out, pc->pin_count);
+    qdev_init_gpio_in(dev, pca9554_gpio_in_handler, pc->pin_count);
 }
 
 static const Property pca9554_properties[] = {
@@ -296,6 +309,7 @@ static void pca9554_class_init(ObjectClass *klass, const void *data)
 {
     DeviceClass *dc = DEVICE_CLASS(klass);
     I2CSlaveClass *k = I2C_SLAVE_CLASS(klass);
+    PCA9554Class *pc = PCA9554_CLASS(klass);
 
     k->event = pca9554_event;
     k->recv = pca9554_recv;
@@ -304,21 +318,32 @@ static void pca9554_class_init(ObjectClass *klass, const void *data)
     device_class_set_legacy_reset(dc, pca9554_reset);
     dc->vmsd = &pca9554_vmstate;
     device_class_set_props(dc, pca9554_properties);
-}
 
-static const TypeInfo pca9554_info = {
-    .name          = TYPE_PCA9554,
-    .parent        = TYPE_I2C_SLAVE,
-    .instance_init = pca9554_initfn,
-    .instance_size = sizeof(PCA9554State),
-    .class_init    = pca9554_class_init,
-    .class_size    = sizeof(PCA9554Class),
-    .abstract      = false,
-};
+    pc->pin_count = PCA9554_PIN_COUNT;
+}
 
-static void pca9554_register_types(void)
+static void pca9536_class_init(ObjectClass *klass, const void *data)
 {
-    type_register_static(&pca9554_info);
+    PCA9554Class *pc = PCA9554_CLASS(klass);
+
+    pc->pin_count = PCA9536_PIN_COUNT;
 }
 
-type_init(pca9554_register_types)
+static const TypeInfo pca9554_types[] = {
+    {
+        .name          = TYPE_PCA9554,
+        .parent        = TYPE_I2C_SLAVE,
+        .instance_init = pca9554_initfn,
+        .instance_size = sizeof(PCA9554State),
+        .class_init    = pca9554_class_init,
+        .class_size    = sizeof(PCA9554Class),
+        .abstract      = false,
+    },
+    {
+        .name          = TYPE_PCA9536,
+        .parent        = TYPE_PCA9554,
+        .class_init    = pca9536_class_init,
+    }
+};
+
+DEFINE_TYPES(pca9554_types);
-- 
2.55.0