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

[Dr. David Alan Gilbert]

* Philippe Mathieu-Daudé (f4bug@amsat.org) wrote:
> On 6/15/20 12:55 PM, Dr. David Alan Gilbert wrote:
> > * 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?
> 
> We model GPIO/IRQ the same way, this is simply a GPIO, right?
> 
> It makes modeling easier IMO. This is for visualization purpose.
> 
> > 
> >> +    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?
> 
> Well I simply wanted to use a boolean, but I need to consider
> if we can model intensity here in case of PWM. This is interesting.

Which then leads to an interesting question about your events in the
next mail;  if I was to connect an LED to a PWM driven GPIO I'd get
zillions of events which may not be what I want.

Dave

> > 
> > 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
> 
> Yes you are right.
> 
> >> +        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.
> 
> Great idea, thanks!
> 
> > 
> > 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
> > 
> 
--
Dr. David Alan Gilbert / dgilbert@redhat.com / Manchester, UK