Re: [Qemu-devel] [RFC v2 1/4] hw/arm/virt: Allow multiple agents to modify dt

[Claudio Fontana <claudio.fontana@huawei.com>]

On 21.11.2014 19:07, Alvise Rigo wrote:
> Keep a global list with all the functions that need to modify the device
> tree.  Using qemu_add_machine_init_done_notifier we register a notifier
> that executes all the functions on the list and loads the kernel.
> 
> Signed-off-by: Alvise Rigo <a.rigo@virtualopensystems.com>

Peter, could you weigh in about whether this is a good idea or not?


> ---
>  hw/arm/virt.c | 55 ++++++++++++++++++++++++++++++++++++++++++++++++++++++-
>  1 file changed, 54 insertions(+), 1 deletion(-)
> 
> diff --git a/hw/arm/virt.c b/hw/arm/virt.c
> index 314e55b..e8d527d 100644
> --- a/hw/arm/virt.c
> +++ b/hw/arm/virt.c
> @@ -70,6 +70,16 @@ enum {
>      VIRT_RTC,
>  };
>  
> +typedef void (*modify_dtb_func)(void *fdt, DeviceState *dev);
> +typedef struct DTModifier {
> +    QLIST_ENTRY(DTModifier) entry;
> +    modify_dtb_func modify_dtb;
> +    DeviceState *dev;
> +} DTModifier;
> +
> +static QLIST_HEAD(, DTModifier) dtb_modifiers =
> +                    QLIST_HEAD_INITIALIZER(dtb_modifiers);
> +
>  typedef struct MemMapEntry {
>      hwaddr base;
>      hwaddr size;
> @@ -149,6 +159,23 @@ static VirtBoardInfo *find_machine_info(const char *cpu)
>      return NULL;
>  }
>  
> +static void add_dtb_modifier(modify_dtb_func func, DeviceState *dev)
> +{
> +    DTModifier *mod_entry = g_new(DTModifier, 1);
> +    mod_entry->modify_dtb = func;
> +    mod_entry->dev = dev;
> +    QLIST_INSERT_HEAD(&dtb_modifiers, mod_entry, entry);
> +}
> +
> +static void free_dtb_modifiers(void)
> +{
> +    while (!QLIST_EMPTY(&dtb_modifiers)) {
> +        DTModifier *modifier = QLIST_FIRST(&dtb_modifiers);
> +        QLIST_REMOVE(modifier, entry);
> +        g_free(modifier);
> +    }
> +}
> +
>  static void create_fdt(VirtBoardInfo *vbi)
>  {
>      void *fdt = create_device_tree(&vbi->fdt_size);
> @@ -527,6 +554,29 @@ static void *machvirt_dtb(const struct arm_boot_info *binfo, int *fdt_size)
>      return board->fdt;
>  }
>  
> +static void machvirt_finalize_dt(Notifier *notify, void *data)
> +{
> +    VirtBoardInfo *vbi;
> +    MachineState *machine;
> +
> +    machine = MACHINE(qdev_get_machine());
> +
> +    vbi = find_machine_info(machine->cpu_model);
> +    if (!vbi) {
> +        vbi = find_machine_info("cortex-a15");
> +    }
> +
> +    struct DTModifier *modifier, *next;
> +    QLIST_FOREACH_SAFE(modifier, &dtb_modifiers, entry, next) {
> +        modifier->modify_dtb(vbi->fdt, modifier->dev);
> +    }
> +
> +    free_dtb_modifiers();
> +
> +    /* Load the kernel only after that the device tree has been modified. */
> +    arm_load_kernel(ARM_CPU(first_cpu), &vbi->bootinfo);
> +}
> +
>  static void machvirt_init(MachineState *machine)
>  {
>      qemu_irq pic[NUM_IRQS];
> @@ -604,6 +654,10 @@ static void machvirt_init(MachineState *machine)
>       */
>      create_virtio_devices(vbi, pic);
>  
> +    Notifier *finalize_dtb_notifier = g_new(Notifier, 1);
> +    finalize_dtb_notifier->notify = machvirt_finalize_dt;
> +    qemu_add_machine_init_done_notifier(finalize_dtb_notifier);
> +
>      vbi->bootinfo.ram_size = machine->ram_size;
>      vbi->bootinfo.kernel_filename = machine->kernel_filename;
>      vbi->bootinfo.kernel_cmdline = machine->kernel_cmdline;
> @@ -612,7 +666,6 @@ static void machvirt_init(MachineState *machine)
>      vbi->bootinfo.board_id = -1;
>      vbi->bootinfo.loader_start = vbi->memmap[VIRT_MEM].base;
>      vbi->bootinfo.get_dtb = machvirt_dtb;
> -    arm_load_kernel(ARM_CPU(first_cpu), &vbi->bootinfo);
>  }
>  
>  static QEMUMachine machvirt_a15_machine = {
>