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

["Michael S. Tsirkin" <mst@redhat.com>]

On Fri, Jan 23, 2015 at 02:32:45PM +0100, Igor Mammedov wrote:
> 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 agree here.

> > 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.

Interesting. where exactly?

> > 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.

OK, I agree.

> > 
> > 
> > > +    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.

0 isn't a valid opcode either, it can really be anything.



> > 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.

"special way" is kind of vague.
Maybe add a comment explaining when it's used.
Is it when length isn't used as a prefix?
AML_NO_PREFIX?


> > 
> > > +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