Re: [PATCH 2/2] hw/adc/npcm7xx_adc.c: convert NPCM7XX_ADC object props to class props

["Daniel P. Berrangé" <berrange@redhat.com>]

On Wed, Jun 24, 2026 at 04:32:30PM +0100, Mark Cave-Ayland wrote:
> Signed-off-by: Mark Cave-Ayland <mark.caveayland@nutanix.com>
> ---
>  hw/adc/npcm7xx_adc.c | 75 +++++++++++++++++++++++++++++++++++++++-----
>  1 file changed, 68 insertions(+), 7 deletions(-)
> 
> diff --git a/hw/adc/npcm7xx_adc.c b/hw/adc/npcm7xx_adc.c
> index 3584c27c75..accaaf2620 100644
> --- a/hw/adc/npcm7xx_adc.c
> +++ b/hw/adc/npcm7xx_adc.c
> @@ -20,6 +20,8 @@
>  #include "hw/core/qdev-properties.h"
>  #include "hw/core/registerfields.h"
>  #include "migration/vmstate.h"
> +#include "qapi/error.h"
> +#include "qapi/visitor.h"
>  #include "qemu/log.h"
>  #include "qemu/module.h"
>  #include "qemu/timer.h"
> @@ -229,7 +231,6 @@ static void npcm7xx_adc_init(Object *obj)
>  {
>      NPCM7xxADCState *s = NPCM7XX_ADC(obj);
>      SysBusDevice *sbd = SYS_BUS_DEVICE(obj);
> -    int i;
>  
>      sysbus_init_irq(sbd, &s->irq);
>  
> @@ -240,15 +241,63 @@ static void npcm7xx_adc_init(Object *obj)
>      sysbus_init_mmio(sbd, &s->iomem);
>      s->clock = qdev_init_clock_in(DEVICE(s), "clock", NULL, NULL, 0);
>  
> -    for (i = 0; i < NPCM7XX_ADC_NUM_INPUTS; ++i) {
> -        object_property_add_uint32_ptr(obj, "adci[*]",
> -                &s->adci[i], OBJ_PROP_FLAG_READWRITE);
> -    }
> -    object_property_add_uint32_ptr(obj, "vref",
> -            &s->vref, OBJ_PROP_FLAG_WRITE);
>      npcm7xx_adc_calibrate(s);
>  }
>  
> +static void npcm7xx_adc_get_input(Object *obj, Visitor *v,
> +                                  const char *name, void *opaque,
> +                                  Error **errp)
> +{
> +    NPCM7xxADCState *s = NPCM7XX_ADC(obj);
> +    uint32_t idx, val;
> +    int res;
> +
> +    res = sscanf(name, "adci[%u]", &idx);
> +    if (res == EOF || res != 1) {
> +        error_setg(errp, "unable to parse index from %s", name);
> +        return;
> +    }
> +
> +    val = s->adci[idx];
> +    visit_type_uint32(v, name, &val, errp);
> +}
> +
> +static void npcm7xx_adc_set_input(Object *obj, Visitor *v,
> +                                  const char *name, void *opaque,
> +                                  Error **errp)
> +{
> +    NPCM7xxADCState *s = NPCM7XX_ADC(obj);
> +    uint32_t idx, val;
> +    int res;
> +
> +    res = sscanf(name, "adci[%u]", &idx);
> +    if (res == EOF || res != 1) {
> +        error_setg(errp, "unable to parse index from %s", name);
> +        return;
> +    }
> +
> +    val = s->adci[idx];
> +    if (!visit_type_uint32(v, name, &val, errp)) {
> +        return;
> +    }
> +
> +    s->adci[idx] = val;
> +}
> +
> +static void npcm7xx_adc_set_vref(Object *obj, Visitor *v,
> +                                 const char *name, void *opaque,
> +                                 Error **errp)
> +{
> +    NPCM7xxADCState *s = NPCM7XX_ADC(obj);
> +    uint32_t vref = s->vref;
> +
> +    if (!visit_type_uint32(v, name, &vref, errp)) {
> +        return;
> +    }
> +
> +    s->vref = vref;
> +}
> +
>  static const VMStateDescription vmstate_npcm7xx_adc = {
>      .name = "npcm7xx-adc",
>      .version_id = 0,
> @@ -275,6 +324,7 @@ static void npcm7xx_adc_class_init(ObjectClass *klass, const void *data)
>  {
>      ResettableClass *rc = RESETTABLE_CLASS(klass);
>      DeviceClass *dc = DEVICE_CLASS(klass);
> +    int i;
>  
>      dc->desc = "NPCM7xx ADC Module";
>      dc->vmsd = &vmstate_npcm7xx_adc;
> @@ -282,6 +332,17 @@ static void npcm7xx_adc_class_init(ObjectClass *klass, const void *data)
>      rc->phases.hold = npcm7xx_adc_hold_reset;
>  
>      device_class_set_props(dc, npcm7xx_timer_properties);
> +
> +    for (i = 0; i < NPCM7XX_ADC_NUM_INPUTS; ++i) {
> +        object_class_property_add(klass, "adci[*]", "uint32",
> +                                  npcm7xx_adc_get_input,
> +                                  npcm7xx_adc_set_input,
> +                                  NULL, NULL);
> +    }

IMHO the logic around "[*]" expansion is mostly useful for child
properties where you don't know ahead of time how many relationships
might already exist.

In this case though, we know exactly how many props we want and we
know we want to start from 0. 

How about we do this explicitly:

   g_autofree char *adciprop = g_strdup_printf("adci[%u]", i);
   object_class_property_add(klass, adciprop, "uint32",
                             npcm7xx_adc_get_input,
                             npcm7xx_adc_set_input,
                             NULL, NULL);

which avoids the O(N^2) performance of handling '[*]' and
thus makes the prior patch redundant.

I kind of wish we didn't have '[' in the property name but
we're probably stuck with that for back compat.

> +    object_class_property_add(klass, "vref", "uint32",
> +                              NULL,
> +                              npcm7xx_adc_set_vref,
> +                              NULL, NULL);
>  }
>  
>  static const TypeInfo npcm7xx_adc_info = {
> -- 
> 2.43.0
> 

With regards,
Daniel
-- 
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