Re: [Qemu-devel] [PATCH v2 06/47] acpi: add acpi_name() & acpi_name_decl() term

[Igor Mammedov <imammedo@redhat.com>]

On Fri, 23 Jan 2015 10:59:48 +0200
"Michael S. Tsirkin" <mst@redhat.com> wrote:

> On Thu, Jan 22, 2015 at 02:49:50PM +0000, Igor Mammedov wrote:
> > Signed-off-by: Igor Mammedov <imammedo@redhat.com>
> > ---
> >  hw/acpi/acpi-build-utils.c         | 24 ++++++++++++++++++++++++
> >  include/hw/acpi/acpi-build-utils.h |  3 +++
> >  2 files changed, 27 insertions(+)
> > 
> > diff --git a/hw/acpi/acpi-build-utils.c b/hw/acpi/acpi-build-utils.c
> > index 40a1769..1bda2ec 100644
> > --- a/hw/acpi/acpi-build-utils.c
> > +++ b/hw/acpi/acpi-build-utils.c
> > @@ -314,6 +314,30 @@ static AcpiAml aml_allocate_internal(uint8_t op, AcpiBlockFlags flags)
> >      return var;
> >  }
> >  
> > +/*
> > + * help to construct NameString, which return AcpiAml object
> > + * for using with other aml_append or other acpi_* terms
> 
> Here and elsewhere: I can't parse this header text.
> I'm guessing you just mean "construct NameString",
> and that's it?
yes

> 
> Also, most other places use build_append_namestring -
> so when should acpi_name be used instead?
> This should be made clear here in the comment.
acpi_name() is a replacement/wrapper around build_append_namestring()
which returns AcpiAml object. build_append_namestring() is a nonpublic
lowlevel helper that deals with GArray,
while acpi_name() follows semantic of AML API.

> 
> > + */
> > +AcpiAml GCC_FMT_ATTR(1, 2) acpi_name(const char *name_format, ...)
> > +{
> 
> This isn't really a name. It just appends a string.  So rename this
> acpi_string and then the below one adding a name can be named acpi_name?
acpi_string is introduced in 27/47, which is a prefixed string
as described in spec.

> Also, in many places one must use only one nameseg.
Where is it exactly?
Perhaps we could build in acpi_name() a check if we know in
what context enforce it. Better to have single/uniform API
for names than a several which is confusing.

> I think a separate api that actually validates
> that it's one segment is better than silently failing.
> Do we ever use it for more than 1 segment?
Yes we use names with more than one segment.

> If not, maybe the right thing to do is
> to use build_append_nameseg and call this one acpi_nameseg.
acpi_name() is used only for passing name as arguments to methods,
in spec there isn't a limitation to only one segment when it comes
to names, in ASL part of it. namesegment however only AML construct
which helps to build name, I prefer not expose lowlevel AML
unless we have to.

> 
> 
> > +    va_list ap;
> > +    AcpiAml var = aml_allocate_internal(0, NON_BLOCK);
> 
> 0 hard coded? What does it mean?
1st arg for NON_BLOCK context doesn't mean anything/ignored.
alternatively I can make aml_allocate_nonblock() wrapper
around generic allocator.

> Same elsewhere.
> 
> > +    va_start(ap, name_format);
> > +    build_append_namestringv(var.buf, name_format, ap);
> > +    va_end(ap);
> > +    return var;
> > +
> > +/* ACPI 5.0: 20.2.5.1 Namespace Modifier Objects Encoding: DefName */
> 
> Let's quote the earliest spec which documents each object:
> one year from now 5.0 will not be the latest.
> Applies here and elsewhere.
> In most places this will be 1.0b.
> Where the construct is newer, this will automatically
> document which guests support it.
I'll try to do it.

> 
> > +AcpiAml acpi_name_decl(const char *name, AcpiAml val)
> > +{
> > +    AcpiAml var = aml_allocate_internal(0, NON_BLOCK);
> > +    build_append_byte(var.buf, 0x08);
> 
> Pls add comment documenting what 0x08 is here.
sure

> 
> > +    build_append_namestring(var.buf, "%s", name);
> > +    aml_append(&var, val);
> > +    return var;
> > +}
> > +
> >  /* ACPI 5.0: 20.2.5.3 Type 1 Opcodes Encoding: DefIfElse */
> >  AcpiAml acpi_if(AcpiAml predicate)
> >  {
> > diff --git a/include/hw/acpi/acpi-build-utils.h b/include/hw/acpi/acpi-build-utils.h
> > index 177f9ed..868cfa5 100644
> > --- a/include/hw/acpi/acpi-build-utils.h
> > +++ b/include/hw/acpi/acpi-build-utils.h
> > @@ -21,6 +21,9 @@ typedef struct AcpiAml {
> >  
> >  void aml_append(AcpiAml *parent_ctx, AcpiAml child);
> >  
> > +/* non block ASL object primitives */
> 
> what does it mean that it's a "non block primitive"?
> I didn't find this concept in the spec.
As for a question what is NON_BLOCK, it's for simple inline ASL
construct that doesn't have to be packaged in special way
examles:
  Store(A,B)
  Name(FOO, VAL)
  IO(...)
while there are different block elements differing in how
they are created see 1/47 aml_append():

ResourceTemplate {
 /* block of other ASL items */
}

Package() {
 /* block of other ASL items */
}

if ... else ...

Scope() {
 /* block of other ASL items */
}

and so on.

> 
> > +AcpiAml GCC_FMT_ATTR(1, 2) acpi_name(const char *name_format, ...);
> > +AcpiAml acpi_name_decl(const char *name, AcpiAml val);
> >  /* Block ASL object primitives */
> >  AcpiAml acpi_if(AcpiAml predicate);
> >  AcpiAml acpi_method(const char *name, int arg_count);
> > -- 
> > 1.8.3.1