Re: [PATCH v4 21/37] sm501: make SerialMM a child, export chardev property

[Peter Maydell <peter.maydell@linaro.org>]

On Wed, 20 Nov 2019 at 15:31, Marc-André Lureau
<marcandre.lureau@redhat.com> wrote:
>
> Embed the SerialMM sybus device, and re-export its "chardev" property.
> That way, we can get rid of PROP_PTR "chr-state" and better track
> devices relationship.
>
> Signed-off-by: Marc-André Lureau <marcandre.lureau@redhat.com>
> ---
>  hw/display/sm501.c | 33 ++++++++++++++++++++++++---------
>  hw/sh4/r2d.c       |  2 +-
>  2 files changed, 25 insertions(+), 10 deletions(-)
>
> diff --git a/hw/display/sm501.c b/hw/display/sm501.c
> index 1f33c87e65..c4445b28f9 100644
> --- a/hw/display/sm501.c
> +++ b/hw/display/sm501.c
> @@ -1930,13 +1930,14 @@ typedef struct {
>      SM501State state;
>      uint32_t vram_size;
>      uint32_t base;
> -    void *chr_state;
> +    SerialMM serial;
>  } SM501SysBusState;
>
>  static void sm501_realize_sysbus(DeviceState *dev, Error **errp)
>  {
>      SM501SysBusState *s = SYSBUS_SM501(dev);
>      SysBusDevice *sbd = SYS_BUS_DEVICE(dev);
> +    SerialState *ss = &s->serial.serial;
>      DeviceState *usb_dev;
>
>      sm501_init(&s->state, dev, s->vram_size);
> @@ -1958,17 +1959,19 @@ static void sm501_realize_sysbus(DeviceState *dev, Error **errp)
>      sysbus_pass_irq(sbd, SYS_BUS_DEVICE(usb_dev));
>
>      /* bridge to serial emulation module */
> -    if (s->chr_state) {
> -        serial_mm_init(&s->state.mmio_region, SM501_UART0, 2,
> -                       NULL, /* TODO : chain irq to IRL */
> -                       115200, s->chr_state, DEVICE_LITTLE_ENDIAN);
> +    /* FIXME: SM501_UART0 is always mapped, no need to check for the backend */
> +    if (qemu_chr_fe_backend_connected(&ss->chr)) {
> +        MemoryRegion *mr;
> +        qdev_init_nofail(DEVICE(&s->serial));
> +        mr = sysbus_mmio_get_region(SYS_BUS_DEVICE(&s->serial), 0);
> +        memory_region_add_subregion(&s->state.mmio_region, SM501_UART0, mr);
> +        /* TODO : chain irq to IRL */
>      }

I don't really understand what the FIXME is trying to
tell me here. If we don't need to check for the backend,
why is the code checking for it ? It means we have to fish
around inside the SerialMM's implementation, which seems odd.
Only mapping the UART registers if there happens to be a backend
connected also doesn't conceptually seem like the right behaviour,
because the registers should always exist. Since commit
12051d82f004024d5d the chardev mid-layer has correctly handled
the backend not being connected (ie having a NULL chardev),
so there's no longer any need for board/device code to special
case the lack of a chardev.

>  }
>
>  static Property sm501_sysbus_properties[] = {
>      DEFINE_PROP_UINT32("vram-size", SM501SysBusState, vram_size, 0),
>      DEFINE_PROP_UINT32("base", SM501SysBusState, base, 0),
> -    DEFINE_PROP_PTR("chr-state", SM501SysBusState, chr_state),
>      DEFINE_PROP_END_OF_LIST(),
>  };
>
> @@ -1999,9 +2002,20 @@ static void sm501_sysbus_class_init(ObjectClass *klass, void *data)
>      dc->props = sm501_sysbus_properties;
>      dc->reset = sm501_reset_sysbus;
>      dc->vmsd = &vmstate_sm501_sysbus;
> -    /* Note: pointer property "chr-state" may remain null, thus
> -     * no need for dc->user_creatable = false;
> -     */
> +}
> +
> +static void sm501_sysbus_init(Object *o)
> +{
> +    SM501SysBusState *sm501 = SYSBUS_SM501(o);
> +    SerialMM *smm = &sm501->serial;
> +
> +    sysbus_init_child_obj(o, "serial", smm, sizeof(SerialMM), TYPE_SERIAL_MM);
> +    qdev_set_legacy_instance_id(DEVICE(smm), SM501_UART0, 2);

The only board we use the sm501 sysbus device is the sh4 r2d
board, and we don't care about migration compatibility there
(indeed I would be unsurprised to find that it doesn't even work ;-))
So I think we can reasonably not set the legacy-instance-ID
and just declare in the commit message that this is a migration
compat break for that board.

> +    qdev_prop_set_uint8(DEVICE(smm), "regshift", 2);
> +    qdev_prop_set_uint8(DEVICE(smm), "endianness", DEVICE_LITTLE_ENDIAN);
> +
> +    object_property_add_alias(o, "chardev",
> +                              OBJECT(smm), "chardev", &error_abort);
>  }
>
>  static const TypeInfo sm501_sysbus_info = {
> @@ -2009,6 +2023,7 @@ static const TypeInfo sm501_sysbus_info = {
>      .parent        = TYPE_SYS_BUS_DEVICE,
>      .instance_size = sizeof(SM501SysBusState),
>      .class_init    = sm501_sysbus_class_init,
> +    .instance_init = sm501_sysbus_init,
>  };
>
>  #define TYPE_PCI_SM501 "sm501"
> diff --git a/hw/sh4/r2d.c b/hw/sh4/r2d.c
> index ee0840f380..72bb5285cc 100644
> --- a/hw/sh4/r2d.c
> +++ b/hw/sh4/r2d.c
> @@ -272,7 +272,7 @@ static void r2d_init(MachineState *machine)
>      busdev = SYS_BUS_DEVICE(dev);
>      qdev_prop_set_uint32(dev, "vram-size", SM501_VRAM_SIZE);
>      qdev_prop_set_uint32(dev, "base", 0x10000000);
> -    qdev_prop_set_ptr(dev, "chr-state", serial_hd(2));
> +    qdev_prop_set_chr(dev, "chardev", serial_hd(2));
>      qdev_init_nofail(dev);
>      sysbus_mmio_map(busdev, 0, 0x10000000);
>      sysbus_mmio_map(busdev, 1, 0x13e00000);
> --
> 2.24.0

thanks
-- PMM