Re: [PATCH v4 13/14] hw/mem/system-memory: add a memory sysbus device

[Igor Mammedov <imammedo@redhat.com>]

On Wed, 23 Feb 2022 10:07:05 +0100
Damien Hedde <damien.hedde@greensocs.com> wrote:

> This device can be used to create a memory wrapped into a
> sysbus device.
> This device has one property 'readonly' which allows
> to choose between a ram or a rom.
> 

> The purpose for this device is to be used with qapi command
> device_add.
that's the way to add a device to QEMU but a don't actual
purpose described here, i.e. how board will use this
device/actual usecase and how it will be wired to board
and why it does have to be a sysbus device.

> Signed-off-by: Damien Hedde <damien.hedde@greensocs.com>
> ---
>  include/hw/mem/sysbus-memory.h | 28 ++++++++++++
>  hw/mem/sysbus-memory.c         | 80 ++++++++++++++++++++++++++++++++++
>  hw/mem/meson.build             |  2 +
>  3 files changed, 110 insertions(+)
>  create mode 100644 include/hw/mem/sysbus-memory.h
>  create mode 100644 hw/mem/sysbus-memory.c
> 
> diff --git a/include/hw/mem/sysbus-memory.h b/include/hw/mem/sysbus-memory.h
> new file mode 100644
> index 0000000000..5c596f8b4f
> --- /dev/null
> +++ b/include/hw/mem/sysbus-memory.h
> @@ -0,0 +1,28 @@
> +/*
> + * SPDX-License-Identifier: GPL-2.0-or-later
> + *
> + * SysBusDevice Memory
> + *
> + * Copyright (c) 2021 Greensocs
> + */
> +
> +#ifndef HW_SYSBUS_MEMORY_H
> +#define HW_SYSBUS_MEMORY_H
> +
> +#include "hw/sysbus.h"
> +#include "qom/object.h"
> +
> +#define TYPE_SYSBUS_MEMORY "sysbus-memory"
> +OBJECT_DECLARE_SIMPLE_TYPE(SysBusMemoryState, SYSBUS_MEMORY)
> +
> +struct SysBusMemoryState {
> +    /* <private> */
> +    SysBusDevice parent_obj;
> +    uint64_t size;
> +    bool readonly;
> +
> +    /* <public> */
> +    MemoryRegion mem;
> +};
> +
> +#endif /* HW_SYSBUS_MEMORY_H */
> diff --git a/hw/mem/sysbus-memory.c b/hw/mem/sysbus-memory.c
> new file mode 100644
> index 0000000000..f1ad7ba7ec
> --- /dev/null
> +++ b/hw/mem/sysbus-memory.c
> @@ -0,0 +1,80 @@
> +/*
> + * SPDX-License-Identifier: GPL-2.0-or-later
> + *
> + * SysBusDevice Memory
> + *
> + * Copyright (c) 2021 Greensocs
> + */
> +
> +#include "qemu/osdep.h"
> +#include "hw/mem/sysbus-memory.h"
> +#include "hw/qdev-properties.h"
> +#include "qemu/log.h"
> +#include "qemu/module.h"
> +#include "qapi/error.h"
> +
> +static Property sysbus_memory_properties[] = {
> +    DEFINE_PROP_UINT64("size", SysBusMemoryState, size, 0),
> +    DEFINE_PROP_BOOL("readonly", SysBusMemoryState, readonly, false),
> +    DEFINE_PROP_END_OF_LIST(),
> +};
> +
> +static void sysbus_memory_realize(DeviceState *dev, Error **errp)
> +{
> +    SysBusMemoryState *s = SYSBUS_MEMORY(dev);
> +    gchar *name;
> +
> +    if (!s->size) {
> +        error_setg(errp, "'size' must be non-zero.");
> +        return;
> +    }
> +
> +    /*
> +     * We impose having an id (which is unique) because we need to generate
> +     * a unique name for the memory region.
> +     * memory_region_init_ram/rom() will abort() (in qemu_ram_set_idstr()
> +     * function if 2 system-memory devices are created with the same name
> +     * for the memory region).
> +     */
> +    if (!dev->id) {
> +        error_setg(errp, "system-memory device must have an id.");
> +        return;
> +    }
> +    name = g_strdup_printf("%s.region", dev->id);
> +
> +    if (s->readonly) {
> +        memory_region_init_rom(&s->mem, OBJECT(dev), name, s->size, errp);
> +    } else {
> +        memory_region_init_ram(&s->mem, OBJECT(dev), name, s->size, errp);
> +    }
> +
> +    g_free(name);
> +    if (*errp) {
> +        return;
> +    }
> +
> +    sysbus_init_mmio(SYS_BUS_DEVICE(s), &s->mem);
> +}
> +
> +static void sysbus_memory_class_init(ObjectClass *klass, void *data)
> +{
> +    DeviceClass *dc = DEVICE_CLASS(klass);
> +
> +    dc->user_creatable = true;
> +    dc->realize = sysbus_memory_realize;
> +    device_class_set_props(dc, sysbus_memory_properties);
> +}
> +
> +static const TypeInfo sysbus_memory_info = {
> +    .name          = TYPE_SYSBUS_MEMORY,
> +    .parent        = TYPE_SYS_BUS_DEVICE,
> +    .instance_size = sizeof(SysBusMemoryState),
> +    .class_init    = sysbus_memory_class_init,
> +};
> +
> +static void sysbus_memory_register_types(void)
> +{
> +    type_register_static(&sysbus_memory_info);
> +}
> +
> +type_init(sysbus_memory_register_types)
> diff --git a/hw/mem/meson.build b/hw/mem/meson.build
> index 82f86d117e..04c74e12f2 100644
> --- a/hw/mem/meson.build
> +++ b/hw/mem/meson.build
> @@ -7,3 +7,5 @@ mem_ss.add(when: 'CONFIG_NVDIMM', if_true: files('nvdimm.c'))
>  softmmu_ss.add_all(when: 'CONFIG_MEM_DEVICE', if_true: mem_ss)
>  
>  softmmu_ss.add(when: 'CONFIG_SPARSE_MEM', if_true: files('sparse-mem.c'))
> +
> +softmmu_ss.add(files('sysbus-memory.c'))