Re: [RFC PATCH v2 1/5] hw/misc: Add a LED device

["Dr. David Alan Gilbert" <dgilbert@redhat.com>]

* Philippe Mathieu-Daudé (f4bug@amsat.org) wrote:
> A LED device can be connected to a GPIO output.
> 
> Signed-off-by: Philippe Mathieu-Daudé <f4bug@amsat.org>
> ---
>  include/hw/misc/led.h | 30 ++++++++++++++++
>  hw/misc/led.c         | 84 +++++++++++++++++++++++++++++++++++++++++++
>  MAINTAINERS           |  6 ++++
>  hw/misc/Kconfig       |  3 ++
>  hw/misc/Makefile.objs |  1 +
>  hw/misc/trace-events  |  3 ++
>  6 files changed, 127 insertions(+)
>  create mode 100644 include/hw/misc/led.h
>  create mode 100644 hw/misc/led.c
> 
> diff --git a/include/hw/misc/led.h b/include/hw/misc/led.h
> new file mode 100644
> index 0000000000..427ca1418e
> --- /dev/null
> +++ b/include/hw/misc/led.h
> @@ -0,0 +1,30 @@
> +/*
> + * 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 "hw/qdev-core.h"
> +#include "hw/sysbus.h" /* FIXME remove */
> +
> +#define TYPE_LED "led"
> +#define LED(obj) OBJECT_CHECK(LEDState, (obj), TYPE_LED)
> +
> +typedef struct LEDState {
> +    /* Private */
> +    SysBusDevice parent_obj; /* FIXME DeviceState */
> +    /* Public */
> +
> +    qemu_irq irq;

Why an irq?

> +    uint8_t current_state;

Is the state of this device boolean or is it a 0..255 0=off, 255=full
on, analog thing?
Can an LED device be connected to a PWM device driving a GPIO - what
happens?

Dave


> +    /* Properties */
> +    char *name;
> +    uint8_t reset_state; /* TODO [GPIO_ACTIVE_LOW, GPIO_ACTIVE_HIGH] */
> +} LEDState;
> +
> +#endif /* HW_MISC_LED_H */
> diff --git a/hw/misc/led.c b/hw/misc/led.c
> new file mode 100644
> index 0000000000..1bae1a34c0
> --- /dev/null
> +++ b/hw/misc/led.c
> @@ -0,0 +1,84 @@
> +/*
> + * 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"
> +
> +static void led_set(void *opaque, int line, int new_state)
> +{
> +    LEDState *s = LED(opaque);
> +
> +    trace_led_set(s->name, s->current_state, new_state);
> +
> +    s->current_state = new_state;
> +}
> +
> +static void led_reset(DeviceState *dev)
> +{
> +    LEDState *s = LED(dev);
> +
> +    led_set(dev, 0, s->reset_state);
> +}
> +
> +static const VMStateDescription vmstate_led = {
> +    .name = TYPE_LED,
> +    .version_id = 1,
> +    .minimum_version_id = 1,
> +    .fields = (VMStateField[]) {
> +        VMSTATE_UINT8(reset_state, LEDState),

I'm not sure you need to migrate this - this is a property that's set on
the device, not a dynamic state of the device
> +        VMSTATE_END_OF_LIST()
> +    }
> +};
> +
> +static void led_realize(DeviceState *dev, Error **errp)
> +{
> +    LEDState *s = LED(dev);
> +
> +    if (s->name == NULL) {
> +        error_setg(errp, "property 'name' not specified");
> +        return;
> +    }
> +
> +    qdev_init_gpio_in(DEVICE(s), led_set, 1);
> +}
> +
> +static Property led_properties[] = {
> +    DEFINE_PROP_STRING("name", LEDState, name),
> +    DEFINE_PROP_UINT8("reset_state", LEDState, reset_state, 0),

I suggest you add a property for the notional colour; that way any UIs
that are built can use that as a hint.

Dave

> +    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_SYS_BUS_DEVICE, /* FIXME 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)
> diff --git a/MAINTAINERS b/MAINTAINERS
> index 3abe3faa4e..10593863dc 100644
> --- a/MAINTAINERS
> +++ b/MAINTAINERS
> @@ -1857,6 +1857,12 @@ 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/misc/Kconfig b/hw/misc/Kconfig
> index bdd77d8020..f60dce694d 100644
> --- a/hw/misc/Kconfig
> +++ b/hw/misc/Kconfig
> @@ -126,6 +126,9 @@ config AUX
>  config UNIMP
>      bool
>  
> +config LED
> +    bool
> +
>  config MAC_VIA
>      bool
>      select MOS6522
> diff --git a/hw/misc/Makefile.objs b/hw/misc/Makefile.objs
> index 5aaca8a039..9efa3c941c 100644
> --- a/hw/misc/Makefile.objs
> +++ b/hw/misc/Makefile.objs
> @@ -91,3 +91,4 @@ common-obj-$(CONFIG_NRF51_SOC) += nrf51_rng.o
>  obj-$(CONFIG_MAC_VIA) += mac_via.o
>  
>  common-obj-$(CONFIG_GRLIB) += grlib_ahb_apb_pnp.o
> +common-obj-$(CONFIG_LED) += led.o
> diff --git a/hw/misc/trace-events b/hw/misc/trace-events
> index 5561746866..e15b7f7c81 100644
> --- a/hw/misc/trace-events
> +++ b/hw/misc/trace-events
> @@ -206,3 +206,6 @@ via1_rtc_cmd_pram_sect_write(int sector, int offset, int addr, int value) "secto
>  # grlib_ahb_apb_pnp.c
>  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(const char *name, uint8_t old_state, uint8_t new_state) "led name:'%s' state %d -> %d"
> -- 
> 2.21.3
> 
--
Dr. David Alan Gilbert / dgilbert@redhat.com / Manchester, UK