Merge remote-tracking branch 'remotes/philmd-gitlab/tags/led-api-20201026' into staging

API to model LED.

CI jobs results:
. https://cirrus-ci.com/build/4879251751043072
. https://gitlab.com/philmd/qemu/-/pipelines/207661784
. https://travis-ci.org/github/philmd/qemu/builds/738958191
. https://app.shippable.com/github/philmd/qemu/runs/891/summary/console

# gpg: Signature made Mon 26 Oct 2020 22:03:59 GMT
# gpg:                using RSA key FAABE75E12917221DCFD6BB2E3E32C2CDEADC0DE
# gpg: Good signature from "Philippe Mathieu-Daudé (F4BUG) <f4bug@amsat.org>" [full]
# Primary key fingerprint: FAAB E75E 1291 7221 DCFD  6BB2 E3E3 2C2C DEAD C0DE

* remotes/philmd-gitlab/tags/led-api-20201026:
  hw/arm/tosa: Replace fprintf() calls by LED devices
  hw/misc/mps2-scc: Use the LED device
  hw/misc/mps2-fpgaio: Use the LED device
  hw/arm/aspeed: Add the 3 front LEDs drived by the PCA9552 #1
  hw/misc/led: Emit a trace event when LED intensity has changed
  hw/misc/led: Allow connecting from GPIO output
  hw/misc/led: Add a LED device

Signed-off-by: Peter Maydell <peter.maydell@linaro.org>

14 files changed, 365 insertions, 43 deletions

diff --git a/MAINTAINERS b/MAINTAINERS
index ef6f5c7..7e442b5 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -1967,6 +1967,12 @@ F: docs/specs/vmgenid.txt
 F: tests/qtest/vmgenid-test.c
 F: stubs/vmgenid.c
 
+LED
+M: Philippe Mathieu-Daudé <f4bug@amsat.org>
+S: Maintained
+F: include/hw/misc/led.h
+F: hw/misc/led.c
+
 Unimplemented device
 M: Peter Maydell <peter.maydell@linaro.org>
 R: Philippe Mathieu-Daudé <f4bug@amsat.org>
diff --git a/hw/arm/Kconfig b/hw/arm/Kconfig
index 7d04082..3c893e0 100644
--- a/hw/arm/Kconfig
+++ b/hw/arm/Kconfig
@@ -151,6 +151,7 @@ config TOSA
     select ZAURUS  # scoop
     select MICRODRIVE
     select PXA2XX
+    select LED
 
 config SPITZ
     bool
@@ -404,6 +405,7 @@ config ASPEED_SOC
     select TMP105
     select TMP421
     select UNIMP
+    select LED
 
 config MPS2
     bool
diff --git a/hw/arm/aspeed.c b/hw/arm/aspeed.c
index bdb981d..0ef3f6b 100644
--- a/hw/arm/aspeed.c
+++ b/hw/arm/aspeed.c
@@ -20,6 +20,7 @@
 #include "hw/i2c/smbus_eeprom.h"
 #include "hw/misc/pca9552.h"
 #include "hw/misc/tmp105.h"
+#include "hw/misc/led.h"
 #include "hw/qdev-properties.h"
 #include "qemu/log.h"
 #include "sysemu/block-backend.h"
@@ -525,9 +526,20 @@ static void sonorapass_bmc_i2c_init(AspeedMachineState *bmc)
 
 static void witherspoon_bmc_i2c_init(AspeedMachineState *bmc)
 {
+    static const struct {
+        unsigned gpio_id;
+        LEDColor color;
+        const char *description;
+        bool gpio_polarity;
+    } pca1_leds[] = {
+        {13, LED_COLOR_GREEN, "front-fault-4",  GPIO_POLARITY_ACTIVE_LOW},
+        {14, LED_COLOR_GREEN, "front-power-3",  GPIO_POLARITY_ACTIVE_LOW},
+        {15, LED_COLOR_GREEN, "front-id-5",     GPIO_POLARITY_ACTIVE_LOW},
+    };
     AspeedSoCState *soc = &bmc->soc;
     uint8_t *eeprom_buf = g_malloc0(8 * 1024);
     DeviceState *dev;
+    LEDState *led;
 
     /* Bus 3: TODO bmp280@77 */
     /* Bus 3: TODO max31785@52 */
@@ -538,6 +550,14 @@ static void witherspoon_bmc_i2c_init(AspeedMachineState *bmc)
                                 aspeed_i2c_get_bus(&soc->i2c, 3),
                                 &error_fatal);
 
+    for (size_t i = 0; i < ARRAY_SIZE(pca1_leds); i++) {
+        led = led_create_simple(OBJECT(bmc),
+                                pca1_leds[i].gpio_polarity,
+                                pca1_leds[i].color,
+                                pca1_leds[i].description);
+        qdev_connect_gpio_out(dev, pca1_leds[i].gpio_id,
+                              qdev_get_gpio_in(DEVICE(led), 0));
+    }
     i2c_slave_create_simple(aspeed_i2c_get_bus(&soc->i2c, 4), "tmp423", 0x4c);
     i2c_slave_create_simple(aspeed_i2c_get_bus(&soc->i2c, 5), "tmp423", 0x4c);
 
diff --git a/hw/arm/tosa.c b/hw/arm/tosa.c
index c196f0d..fe88ed8 100644
--- a/hw/arm/tosa.c
+++ b/hw/arm/tosa.c
@@ -24,6 +24,7 @@
 #include "hw/irq.h"
 #include "hw/ssi/ssi.h"
 #include "hw/sysbus.h"
+#include "hw/misc/led.h"
 #include "exec/address-spaces.h"
 #include "qom/object.h"
 
@@ -81,26 +82,6 @@ struct TosaMiscGPIOState {
     SysBusDevice parent_obj;
 };
 
-static void tosa_gpio_leds(void *opaque, int line, int level)
-{
-    switch (line) {
-    case 0:
-        fprintf(stderr, "blue LED %s.\n", level ? "on" : "off");
-        break;
-    case 1:
-        fprintf(stderr, "green LED %s.\n", level ? "on" : "off");
-        break;
-    case 2:
-        fprintf(stderr, "amber LED %s.\n", level ? "on" : "off");
-        break;
-    case 3:
-        fprintf(stderr, "wlan LED %s.\n", level ? "on" : "off");
-        break;
-    default:
-        g_assert_not_reached();
-    }
-}
-
 static void tosa_reset(void *opaque, int line, int level)
 {
     if (level) {
@@ -112,7 +93,6 @@ static void tosa_misc_gpio_init(Object *obj)
 {
     DeviceState *dev = DEVICE(obj);
 
-    qdev_init_gpio_in_named(dev, tosa_gpio_leds, "leds", 4);
     qdev_init_gpio_in_named(dev, tosa_reset, "reset", 1);
 }
 
@@ -122,6 +102,7 @@ static void tosa_gpio_setup(PXA2xxState *cpu,
                 TC6393xbState *tmio)
 {
     DeviceState *misc_gpio;
+    LEDState *led[4];
 
     misc_gpio = sysbus_create_simple(TYPE_TOSA_MISC_GPIO, -1, NULL);
 
@@ -143,14 +124,23 @@ static void tosa_gpio_setup(PXA2xxState *cpu,
                         qdev_get_gpio_in(cpu->gpio, TOSA_GPIO_JC_CF_IRQ),
                         NULL);
 
+    led[0] = led_create_simple(OBJECT(misc_gpio), GPIO_POLARITY_ACTIVE_HIGH,
+                               LED_COLOR_BLUE, "bluetooth");
+    led[1] = led_create_simple(OBJECT(misc_gpio), GPIO_POLARITY_ACTIVE_HIGH,
+                               LED_COLOR_GREEN, "note");
+    led[2] = led_create_simple(OBJECT(misc_gpio), GPIO_POLARITY_ACTIVE_HIGH,
+                               LED_COLOR_AMBER, "charger-error");
+    led[3] = led_create_simple(OBJECT(misc_gpio), GPIO_POLARITY_ACTIVE_HIGH,
+                               LED_COLOR_GREEN, "wlan");
+
     qdev_connect_gpio_out(scp1, TOSA_GPIO_BT_LED,
-                          qdev_get_gpio_in_named(misc_gpio, "leds", 0));
+                          qdev_get_gpio_in(DEVICE(led[0]), 0));
     qdev_connect_gpio_out(scp1, TOSA_GPIO_NOTE_LED,
-                          qdev_get_gpio_in_named(misc_gpio, "leds", 1));
+                          qdev_get_gpio_in(DEVICE(led[1]), 0));
     qdev_connect_gpio_out(scp1, TOSA_GPIO_CHRG_ERR_LED,
-                          qdev_get_gpio_in_named(misc_gpio, "leds", 2));
+                          qdev_get_gpio_in(DEVICE(led[2]), 0));
     qdev_connect_gpio_out(scp1, TOSA_GPIO_WLAN_LED,
-                          qdev_get_gpio_in_named(misc_gpio, "leds", 3));
+                          qdev_get_gpio_in(DEVICE(led[3]), 0));
 
     qdev_connect_gpio_out(scp1, TOSA_GPIO_TC6393XB_L3V_ON, tc6393xb_l3v_get(tmio));
 
diff --git a/hw/misc/Kconfig b/hw/misc/Kconfig
index 3185456..877ecff 100644
--- a/hw/misc/Kconfig
+++ b/hw/misc/Kconfig
@@ -93,9 +93,11 @@ config MIPS_ITU
 
 config MPS2_FPGAIO
     bool
+    select LED
 
 config MPS2_SCC
     bool
+    select LED
 
 config TZ_MPC
     bool
@@ -126,6 +128,9 @@ config AUX
 config UNIMP
     bool
 
+config LED
+    bool
+
 config MAC_VIA
     bool
     select MOS6522
diff --git a/hw/misc/led.c b/hw/misc/led.c
new file mode 100644
index 0000000..5266d02
--- /dev/null
+++ b/hw/misc/led.c
@@ -0,0 +1,161 @@
+/*
+ * QEMU single LED device
+ *
+ * Copyright (C) 2020 Philippe Mathieu-Daudé <f4bug@amsat.org>
+ *
+ * SPDX-License-Identifier: GPL-2.0-or-later
+ */
+#include "qemu/osdep.h"
+#include "qapi/error.h"
+#include "migration/vmstate.h"
+#include "hw/qdev-properties.h"
+#include "hw/misc/led.h"
+#include "hw/irq.h"
+#include "trace.h"
+
+#define LED_INTENSITY_PERCENT_MAX   100
+
+static const char * const led_color_name[] = {
+    [LED_COLOR_VIOLET]  = "violet",
+    [LED_COLOR_BLUE]    = "blue",
+    [LED_COLOR_CYAN]    = "cyan",
+    [LED_COLOR_GREEN]   = "green",
+    [LED_COLOR_AMBER]   = "amber",
+    [LED_COLOR_ORANGE]  = "orange",
+    [LED_COLOR_RED]     = "red",
+};
+
+static bool led_color_name_is_valid(const char *color_name)
+{
+    for (size_t i = 0; i < ARRAY_SIZE(led_color_name); i++) {
+        if (strcmp(color_name, led_color_name[i]) == 0) {
+            return true;
+        }
+    }
+    return false;
+}
+
+void led_set_intensity(LEDState *s, unsigned intensity_percent)
+{
+    if (intensity_percent > LED_INTENSITY_PERCENT_MAX) {
+        intensity_percent = LED_INTENSITY_PERCENT_MAX;
+    }
+    trace_led_set_intensity(s->description, s->color, intensity_percent);
+    if (intensity_percent != s->intensity_percent) {
+        trace_led_change_intensity(s->description, s->color,
+                                   s->intensity_percent, intensity_percent);
+    }
+    s->intensity_percent = intensity_percent;
+}
+
+unsigned led_get_intensity(LEDState *s)
+{
+    return s->intensity_percent;
+}
+
+void led_set_state(LEDState *s, bool is_emitting)
+{
+    led_set_intensity(s, is_emitting ? LED_INTENSITY_PERCENT_MAX : 0);
+}
+
+static void led_set_state_gpio_handler(void *opaque, int line, int new_state)
+{
+    LEDState *s = LED(opaque);
+
+    assert(line == 0);
+    led_set_state(s, !!new_state != s->gpio_active_high);
+}
+
+static void led_reset(DeviceState *dev)
+{
+    LEDState *s = LED(dev);
+
+    led_set_state(s, s->gpio_active_high);
+}
+
+static const VMStateDescription vmstate_led = {
+    .name = TYPE_LED,
+    .version_id = 1,
+    .minimum_version_id = 1,
+    .fields = (VMStateField[]) {
+        VMSTATE_UINT8(intensity_percent, LEDState),
+        VMSTATE_END_OF_LIST()
+    }
+};
+
+static void led_realize(DeviceState *dev, Error **errp)
+{
+    LEDState *s = LED(dev);
+
+    if (s->color == NULL) {
+        error_setg(errp, "property 'color' not specified");
+        return;
+    } else if (!led_color_name_is_valid(s->color)) {
+        error_setg(errp, "property 'color' invalid or not supported");
+        return;
+    }
+    if (s->description == NULL) {
+        s->description = g_strdup("n/a");
+    }
+
+    qdev_init_gpio_in(DEVICE(s), led_set_state_gpio_handler, 1);
+}
+
+static Property led_properties[] = {
+    DEFINE_PROP_STRING("color", LEDState, color),
+    DEFINE_PROP_STRING("description", LEDState, description),
+    DEFINE_PROP_BOOL("gpio-active-high", LEDState, gpio_active_high, true),
+    DEFINE_PROP_END_OF_LIST(),
+};
+
+static void led_class_init(ObjectClass *klass, void *data)
+{
+    DeviceClass *dc = DEVICE_CLASS(klass);
+
+    dc->desc = "LED";
+    dc->vmsd = &vmstate_led;
+    dc->reset = led_reset;
+    dc->realize = led_realize;
+    set_bit(DEVICE_CATEGORY_DISPLAY, dc->categories);
+    device_class_set_props(dc, led_properties);
+}
+
+static const TypeInfo led_info = {
+    .name = TYPE_LED,
+    .parent = TYPE_DEVICE,
+    .instance_size = sizeof(LEDState),
+    .class_init = led_class_init
+};
+
+static void led_register_types(void)
+{
+    type_register_static(&led_info);
+}
+
+type_init(led_register_types)
+
+LEDState *led_create_simple(Object *parentobj,
+                            GpioPolarity gpio_polarity,
+                            LEDColor color,
+                            const char *description)
+{
+    g_autofree char *name = NULL;
+    DeviceState *dev;
+
+    dev = qdev_new(TYPE_LED);
+    qdev_prop_set_bit(dev, "gpio-active-high",
+                      gpio_polarity == GPIO_POLARITY_ACTIVE_HIGH);
+    qdev_prop_set_string(dev, "color", led_color_name[color]);
+    if (!description) {
+        static unsigned undescribed_led_id;
+        name = g_strdup_printf("undescribed-led-#%u", undescribed_led_id++);
+    } else {
+        qdev_prop_set_string(dev, "description", description);
+        name = g_ascii_strdown(description, -1);
+        name = g_strdelimit(name, " #", '-');
+    }
+    object_property_add_child(parentobj, name, OBJECT(dev));
+    qdev_realize_and_unref(dev, NULL, &error_fatal);
+
+    return LED(dev);
+}
diff --git a/hw/misc/meson.build b/hw/misc/meson.build
index 793d45b..aa8ec3b 100644
--- a/hw/misc/meson.build
+++ b/hw/misc/meson.build
@@ -11,6 +11,7 @@ softmmu_ss.add(when: 'CONFIG_TMP105', if_true: files('tmp105.c'))
 softmmu_ss.add(when: 'CONFIG_TMP421', if_true: files('tmp421.c'))
 softmmu_ss.add(when: 'CONFIG_UNIMP', if_true: files('unimp.c'))
 softmmu_ss.add(when: 'CONFIG_EMPTY_SLOT', if_true: files('empty_slot.c'))
+softmmu_ss.add(when: 'CONFIG_LED', if_true: files('led.c'))
 
 # ARM devices
 softmmu_ss.add(when: 'CONFIG_PL310', if_true: files('arm_l2x0.c'))
diff --git a/hw/misc/mps2-fpgaio.c b/hw/misc/mps2-fpgaio.c
index 2f3fbee..6af0e8f 100644
--- a/hw/misc/mps2-fpgaio.c
+++ b/hw/misc/mps2-fpgaio.c
@@ -24,6 +24,7 @@
 #include "migration/vmstate.h"
 #include "hw/registerfields.h"
 #include "hw/misc/mps2-fpgaio.h"
+#include "hw/misc/led.h"
 #include "hw/qdev-properties.h"
 #include "qemu/timer.h"
 
@@ -176,12 +177,9 @@ static void mps2_fpgaio_write(void *opaque, hwaddr offset, uint64_t value,
 
     switch (offset) {
     case A_LED0:
-        /* LED bits [1:0] control board LEDs. We don't currently have
-         * a mechanism for displaying this graphically, so use a trace event.
-         */
-        trace_mps2_fpgaio_leds(value & 0x02 ? '*' : '.',
-                               value & 0x01 ? '*' : '.');
         s->led0 = value & 0x3;
+        led_set_state(s->led[0], value & 0x01);
+        led_set_state(s->led[1], value & 0x02);
         break;
     case A_PRESCALE:
         resync_counter(s);
@@ -239,6 +237,10 @@ static void mps2_fpgaio_reset(DeviceState *dev)
     s->counter = 0;
     s->pscntr = 0;
     s->pscntr_sync_ticks = now;
+
+    for (size_t i = 0; i < ARRAY_SIZE(s->led); i++) {
+        device_cold_reset(DEVICE(s->led[i]));
+    }
 }
 
 static void mps2_fpgaio_init(Object *obj)
@@ -251,6 +253,16 @@ static void mps2_fpgaio_init(Object *obj)
     sysbus_init_mmio(sbd, &s->iomem);
 }
 
+static void mps2_fpgaio_realize(DeviceState *dev, Error **errp)
+{
+    MPS2FPGAIO *s = MPS2_FPGAIO(dev);
+
+    s->led[0] = led_create_simple(OBJECT(dev), GPIO_POLARITY_ACTIVE_HIGH,
+                                  LED_COLOR_GREEN, "USERLED0");
+    s->led[1] = led_create_simple(OBJECT(dev), GPIO_POLARITY_ACTIVE_HIGH,
+                                  LED_COLOR_GREEN, "USERLED1");
+}
+
 static bool mps2_fpgaio_counters_needed(void *opaque)
 {
     /* Currently vmstate.c insists all subsections have a 'needed' function */
@@ -299,6 +311,7 @@ static void mps2_fpgaio_class_init(ObjectClass *klass, void *data)
     DeviceClass *dc = DEVICE_CLASS(klass);
 
     dc->vmsd = &mps2_fpgaio_vmstate;
+    dc->realize = mps2_fpgaio_realize;
     dc->reset = mps2_fpgaio_reset;
     device_class_set_props(dc, mps2_fpgaio_properties);
 }
diff --git a/hw/misc/mps2-scc.c b/hw/misc/mps2-scc.c
index 9d0909e..ce1dfe9 100644
--- a/hw/misc/mps2-scc.c
+++ b/hw/misc/mps2-scc.c
@@ -20,11 +20,13 @@
 #include "qemu/osdep.h"
 #include "qemu/log.h"
 #include "qemu/module.h"
+#include "qemu/bitops.h"
 #include "trace.h"
 #include "hw/sysbus.h"
 #include "migration/vmstate.h"
 #include "hw/registerfields.h"
 #include "hw/misc/mps2-scc.h"
+#include "hw/misc/led.h"
 #include "hw/qdev-properties.h"
 
 REG32(CFG0, 0)
@@ -152,18 +154,10 @@ static void mps2_scc_write(void *opaque, hwaddr offset, uint64_t value,
         s->cfg0 = value;
         break;
     case A_CFG1:
-        /* CFG1 bits [7:0] control the board LEDs. We don't currently have
-         * a mechanism for displaying this graphically, so use a trace event.
-         */
-        trace_mps2_scc_leds(value & 0x80 ? '*' : '.',
-                            value & 0x40 ? '*' : '.',
-                            value & 0x20 ? '*' : '.',
-                            value & 0x10 ? '*' : '.',
-                            value & 0x08 ? '*' : '.',
-                            value & 0x04 ? '*' : '.',
-                            value & 0x02 ? '*' : '.',
-                            value & 0x01 ? '*' : '.');
         s->cfg1 = value;
+        for (size_t i = 0; i < ARRAY_SIZE(s->led); i++) {
+            led_set_state(s->led[i], extract32(value, i, 1));
+        }
         break;
     case A_CFGDATA_OUT:
         s->cfgdata_out = value;
@@ -236,6 +230,9 @@ static void mps2_scc_reset(DeviceState *dev)
     for (i = 0; i < NUM_OSCCLK; i++) {
         s->oscclk[i] = s->oscclk_reset[i];
     }
+    for (i = 0; i < ARRAY_SIZE(s->led); i++) {
+        device_cold_reset(DEVICE(s->led[i]));
+    }
 }
 
 static void mps2_scc_init(Object *obj)
@@ -249,6 +246,14 @@ static void mps2_scc_init(Object *obj)
 
 static void mps2_scc_realize(DeviceState *dev, Error **errp)
 {
+    MPS2SCC *s = MPS2_SCC(dev);
+
+    for (size_t i = 0; i < ARRAY_SIZE(s->led); i++) {
+        char *name = g_strdup_printf("SCC LED%zu", i);
+        s->led[i] = led_create_simple(OBJECT(dev), GPIO_POLARITY_ACTIVE_HIGH,
+                                      LED_COLOR_GREEN, name);
+        g_free(name);
+    }
 }
 
 static const VMStateDescription mps2_scc_vmstate = {
diff --git a/hw/misc/trace-events b/hw/misc/trace-events
index 6054f9a..c68811b 100644
--- a/hw/misc/trace-events
+++ b/hw/misc/trace-events
@@ -84,7 +84,6 @@ aspeed_scu_write(uint64_t offset, unsigned size, uint32_t data) "To 0x%" PRIx64
 mps2_scc_read(uint64_t offset, uint64_t data, unsigned size) "MPS2 SCC read: offset 0x%" PRIx64 " data 0x%" PRIx64 " size %u"
 mps2_scc_write(uint64_t offset, uint64_t data, unsigned size) "MPS2 SCC write: offset 0x%" PRIx64 " data 0x%" PRIx64 " size %u"
 mps2_scc_reset(void) "MPS2 SCC: reset"
-mps2_scc_leds(char led7, char led6, char led5, char led4, char led3, char led2, char led1, char led0) "MPS2 SCC LEDs: %c%c%c%c%c%c%c%c"
 mps2_scc_cfg_write(unsigned function, unsigned device, uint32_t value) "MPS2 SCC config write: function %d device %d data 0x%" PRIx32
 mps2_scc_cfg_read(unsigned function, unsigned device, uint32_t value) "MPS2 SCC config read: function %d device %d data 0x%" PRIx32
 
@@ -92,7 +91,6 @@ mps2_scc_cfg_read(unsigned function, unsigned device, uint32_t value) "MPS2 SCC
 mps2_fpgaio_read(uint64_t offset, uint64_t data, unsigned size) "MPS2 FPGAIO read: offset 0x%" PRIx64 " data 0x%" PRIx64 " size %u"
 mps2_fpgaio_write(uint64_t offset, uint64_t data, unsigned size) "MPS2 FPGAIO write: offset 0x%" PRIx64 " data 0x%" PRIx64 " size %u"
 mps2_fpgaio_reset(void) "MPS2 FPGAIO: reset"
-mps2_fpgaio_leds(char led1, char led0) "MPS2 FPGAIO LEDs: %c%c"
 
 # msf2-sysreg.c
 msf2_sysreg_write(uint64_t offset, uint32_t val, uint32_t prev) "msf2-sysreg write: addr 0x%08" PRIx64 " data 0x%" PRIx32 " prev 0x%" PRIx32
@@ -223,6 +221,10 @@ via1_adb_poll(uint8_t data, const char *vadbint, int status, int index, int size
 grlib_ahb_pnp_read(uint64_t addr, uint32_t value) "AHB PnP read addr:0x%03"PRIx64" data:0x%08x"
 grlib_apb_pnp_read(uint64_t addr, uint32_t value) "APB PnP read addr:0x%03"PRIx64" data:0x%08x"
 
+# led.c
+led_set_intensity(const char *color, const char *desc, uint8_t intensity_percent) "LED desc:'%s' color:%s intensity: %u%%"
+led_change_intensity(const char *color, const char *desc, uint8_t old_intensity_percent, uint8_t new_intensity_percent) "LED desc:'%s' color:%s intensity %u%% -> %u%%"
+
 # pca9552.c
 pca955x_gpio_status(const char *description, const char *buf) "%s GPIOs 0-15 [%s]"
 pca955x_gpio_change(const char *description, unsigned id, unsigned prev_state, unsigned current_state) "%s GPIO id:%u status: %u -> %u"
diff --git a/include/hw/misc/led.h b/include/hw/misc/led.h
new file mode 100644
index 0000000..aa359b8
--- /dev/null
+++ b/include/hw/misc/led.h
@@ -0,0 +1,97 @@
+/*
+ * QEMU single LED device
+ *
+ * Copyright (C) 2020 Philippe Mathieu-Daudé <f4bug@amsat.org>
+ *
+ * SPDX-License-Identifier: GPL-2.0-or-later
+ */
+#ifndef HW_MISC_LED_H
+#define HW_MISC_LED_H
+
+#include "qom/object.h"
+#include "hw/qdev-core.h"
+
+#define TYPE_LED "led"
+
+/**
+ * LEDColor: Color of a LED
+ *
+ * This set is restricted to physically available LED colors.
+ *
+ * LED colors from 'Table 1. Product performance of LUXEON Rebel Color
+ * Line' of the 'DS68 LUXEON Rebel Color Line' datasheet available at:
+ * https://www.lumileds.com/products/color-leds/luxeon-rebel-color/
+ */
+typedef enum {          /* Coarse wavelength range */
+    LED_COLOR_VIOLET,   /* 425 nm */
+    LED_COLOR_BLUE,     /* 475 nm */
+    LED_COLOR_CYAN,     /* 500 nm */
+    LED_COLOR_GREEN,    /* 535 nm */
+    LED_COLOR_AMBER,    /* 590 nm */
+    LED_COLOR_ORANGE,   /* 615 nm */
+    LED_COLOR_RED,      /* 630 nm */
+} LEDColor;
+
+struct LEDState {
+    /* Private */
+    DeviceState parent_obj;
+    /* Public */
+
+    uint8_t intensity_percent;
+    qemu_irq irq;
+
+    /* Properties */
+    char *description;
+    char *color;
+    /*
+     * Determines whether a GPIO is using a positive (active-high)
+     * logic (when used with GPIO, the intensity at reset is related
+     * to the GPIO polarity).
+     */
+    bool gpio_active_high;
+};
+typedef struct LEDState LEDState;
+DECLARE_INSTANCE_CHECKER(LEDState, LED, TYPE_LED)
+
+/**
+ * led_set_intensity: Set the intensity of a LED device
+ * @s: the LED object
+ * @intensity_percent: intensity as percentage in range 0 to 100.
+ */
+void led_set_intensity(LEDState *s, unsigned intensity_percent);
+
+/**
+ * led_get_intensity:
+ * @s: the LED object
+ *
+ * Returns: The LED intensity as percentage in range 0 to 100.
+ */
+unsigned led_get_intensity(LEDState *s);
+
+/**
+ * led_set_state: Set the state of a LED device
+ * @s: the LED object
+ * @is_emitting: boolean indicating whether the LED is emitting
+ *
+ * This utility is meant for LED connected to GPIO.
+ */
+void led_set_state(LEDState *s, bool is_emitting);
+
+/**
+ * led_create_simple: Create and realize a LED device
+ * @parentobj: the parent object
+ * @gpio_polarity: GPIO polarity
+ * @color: color of the LED
+ * @description: description of the LED (optional)
+ *
+ * Create the device state structure, initialize it, and
+ * drop the reference to it (the device is realized).
+ *
+ * Returns: The newly allocated and instantiated LED object.
+ */
+LEDState *led_create_simple(Object *parentobj,
+                            GpioPolarity gpio_polarity,
+                            LEDColor color,
+                            const char *description);
+
+#endif /* HW_MISC_LED_H */
diff --git a/include/hw/misc/mps2-fpgaio.h b/include/hw/misc/mps2-fpgaio.h
index 80f9227..a010fdb 100644
--- a/include/hw/misc/mps2-fpgaio.h
+++ b/include/hw/misc/mps2-fpgaio.h
@@ -22,6 +22,7 @@
 #define MPS2_FPGAIO_H
 
 #include "hw/sysbus.h"
+#include "hw/misc/led.h"
 #include "qom/object.h"
 
 #define TYPE_MPS2_FPGAIO "mps2-fpgaio"
@@ -33,6 +34,7 @@ struct MPS2FPGAIO {
 
     /*< public >*/
     MemoryRegion iomem;
+    LEDState *led[2];
 
     uint32_t led0;
     uint32_t prescale;
diff --git a/include/hw/misc/mps2-scc.h b/include/hw/misc/mps2-scc.h
index e922b3c..f65d873 100644
--- a/include/hw/misc/mps2-scc.h
+++ b/include/hw/misc/mps2-scc.h
@@ -13,6 +13,7 @@
 #define MPS2_SCC_H
 
 #include "hw/sysbus.h"
+#include "hw/misc/led.h"
 #include "qom/object.h"
 
 #define TYPE_MPS2_SCC "mps2-scc"
@@ -26,6 +27,7 @@ struct MPS2SCC {
 
     /*< public >*/
     MemoryRegion iomem;
+    LEDState *led[8];
 
     uint32_t cfg0;
     uint32_t cfg1;
diff --git a/include/hw/qdev-core.h b/include/hw/qdev-core.h
index 8689733..a653295 100644
--- a/include/hw/qdev-core.h
+++ b/include/hw/qdev-core.h
@@ -444,6 +444,22 @@ void qdev_machine_creation_done(void);
 bool qdev_machine_modified(void);
 
 /**
+ * GpioPolarity: Polarity of a GPIO line
+ *
+ * GPIO lines use either positive (active-high) logic,
+ * or negative (active-low) logic.
+ *
+ * In active-high logic (%GPIO_POLARITY_ACTIVE_HIGH), a pin is
+ * active when the voltage on the pin is high (relative to ground);
+ * whereas in active-low logic (%GPIO_POLARITY_ACTIVE_LOW), a pin
+ * is active when the voltage on the pin is low (or grounded).
+ */
+typedef enum {
+    GPIO_POLARITY_ACTIVE_LOW,
+    GPIO_POLARITY_ACTIVE_HIGH
+} GpioPolarity;
+
+/**
  * qdev_get_gpio_in: Get one of a device's anonymous input GPIO lines
  * @dev: Device whose GPIO we want
  * @n: Number of the anonymous GPIO line (which must be in range)