Re: [Qemu-devel] [PATCH v2 01/47] acpi: introduce AML composer aml_append()

[Igor Mammedov]

On Wed, 28 Jan 2015 09:56:26 +0200
"Michael S. Tsirkin" <address@hidden> wrote:

> > I've tried redo series with passing alloc list as first argument,
> > looks ugly as hell
> 
> I tried too. Not too bad at all. See below:
> 
> diff --git a/hw/i386/acpi-build.c b/hw/i386/acpi-build.c
> index f66da5d..820504a 100644
> --- a/hw/i386/acpi-build.c
> +++ b/hw/i386/acpi-build.c
> @@ -491,14 +491,14 @@ static void acpi_set_pci_info(void)
>      }
>  }
>  
> -static void build_append_pcihp_notify_entry(AcpiAml *method, int slot)
> +static void build_append_pcihp_notify_entry(AmlPool *p, AcpiAml *method, int 
> slot)
>  {
> -    AcpiAml if_ctx;
> +    AcpiAml *if_ctx;
>      int32_t devfn = PCI_DEVFN(slot, 0);
>  
> -    if_ctx = acpi_if(acpi_and(acpi_arg0(), acpi_int(0x1U << slot)));
> -    aml_append(&if_ctx, acpi_notify(acpi_name("S%.02X", devfn), 
> acpi_arg1()));
> -    aml_append(method, if_ctx);
> +    if_ctx = acpi_if(p, acpi_and(p, acpi_arg0(), acpi_int(p, 0x1U << slot)));
> +    aml_append(p, if_ctx, acpi_notify(p, acpi_name(p, "S%.02X", devfn), 
> acpi_arg1(p)));
> +    aml_append(p, method, if_ctx);
>  }
>  
>  static void build_append_pci_bus_devices(AcpiAml *parent_scope, PCIBus *bus,
> 
> What exactly is the problem?  A tiny bit more verbose but the lifetime
> of all objects is now explicit.
every usage of aml_foo()/build_append_pcihp_notify_entry() tags along
extra pointer which is not really necessary for user to know. If possible
user shouldn't care about it and concentrate on composing AML instead.

Whole point of passing AmlPool and record every allocation is to avoid
mistakes like:

acpi_if(acpi_and(acpi_arg0(), acpi_int(0x1U << slot)));

and forgetting to assign object returned by call anywhere,
it's basically the same as calling malloc() without
using result anywhere, however neither libc nor glib
force user to pass allocator (in our case garbage collector)
in every call that allocates memory. Let's just follow common
convention here (#4) where an object is allocated by API call
(i.e like object_new(FOO), gtk_widget_foo()).

Hence is suggesting at least to hide AmlPool internally in API
without exposing it to user. We can provide for user
init/free API to manage internal AmlPool manually, allowing
him to select when to do initialization and cleanup.

Claudio, Marcel, Shannon,
As the first API users, could you give your feedback on the topic.