Re: [PATCH RFC net-next v2 2/3] vsock/test: Introduce get_transports()

[Stefano Garzarella]

On Fri, Jun 06, 2025 at 09:51:29AM +0200, Michal Luczaj wrote:
> On 6/5/25 12:46, Stefano Garzarella wrote:
> > On Wed, Jun 04, 2025 at 09:10:19PM +0200, Michal Luczaj wrote:
> > > On 6/4/25 11:07, Stefano Garzarella wrote:
> > > > On Wed, May 28, 2025 at 10:44:42PM +0200, Michal Luczaj wrote:
> > > > > +static int __get_transports(void)
> > > > > +{
> > > > > +	/* Order must match transports defined in util.h.
> > > > > +	 * man nm: "d" The symbol is in the initialized data section.
> > > > > +	 */
> > > > > +	const char * const syms[] = {
> > > > > +		"d loopback_transport",
> > > > > +		"d virtio_transport",
> > > > > +		"d vhost_transport",
> > > > > +		"d vmci_transport",
> > > > > +		"d hvs_transport",
> > > > > +	};
> > > >
> > > > I would move this array (or a macro that define it), near the transport
> > > > defined in util.h, so they are near and we can easily update/review
> > > > changes.
> > > >
> > > > BTW what about adding static asserts to check we are aligned?
> > >
> > > Something like
> > >
> > > #define KNOWN_TRANSPORTS	\
> >
> > What about KNOWN_TRANSPORTS(_) ?
>
> Ah, yeah.
>
> > > 	_(LOOPBACK, "loopback")	\
> > > 	_(VIRTIO, "virtio")	\
> > > 	_(VHOST, "vhost")	\
> > > 	_(VMCI, "vmci")		\
> > > 	_(HYPERV, "hvs")
> > >
> > > enum transport {
> > > 	TRANSPORT_COUNTER_BASE = __COUNTER__ + 1,
> > > 	#define _(name, symbol)	\
> > > 		TRANSPORT_##name = _BITUL(__COUNTER__ - TRANSPORT_COUNTER_BASE),
> > > 	KNOWN_TRANSPORTS
> > > 	TRANSPORT_NUM = __COUNTER__ - TRANSPORT_COUNTER_BASE,
> > > 	#undef _
> > > };
> > >
> > > static char * const transport_ksyms[] = {
> > > 	#define _(name, symbol) "d " symbol "_transport",
> > > 	KNOWN_TRANSPORTS
> > > 	#undef _
> > > };
> > >
> > > static_assert(ARRAY_SIZE(transport_ksyms) == TRANSPORT_NUM);
> > >
> > > ?
> >
> > Yep, this is even better, thanks :-)
>
> Although checkpatch complains:
>
> ERROR: Macros with complex values should be enclosed in parentheses
> #105: FILE: tools/testing/vsock/util.h:11:
> +#define KNOWN_TRANSPORTS(_)	\
> +	_(LOOPBACK, "loopback")	\
> +	_(VIRTIO, "virtio")	\
> +	_(VHOST, "vhost")	\
> +	_(VMCI, "vmci")		\
> +	_(HYPERV, "hvs")
>
> BUT SEE:
>
>   do {} while (0) advice is over-stated in a few situations:
>
>   The more obvious case is macros, like MODULE_PARM_DESC, invoked at
>   file-scope, where C disallows code (it must be in functions).  See
>   $exceptions if you have one to add by name.
>
>   More troublesome is declarative macros used at top of new scope,
>   like DECLARE_PER_CPU.  These might just compile with a do-while-0
>   wrapper, but would be incorrect.  Most of these are handled by
>   detecting struct,union,etc declaration primitives in $exceptions.
>
>   Theres also macros called inside an if (block), which "return" an
>   expression.  These cannot do-while, and need a ({}) wrapper.
>
>   Enjoy this qualification while we work to improve our heuristics.
>
> ERROR: Macros with complex values should be enclosed in parentheses
> #114: FILE: tools/testing/vsock/util.h:20:
> +	#define _(name, symbol)	\
> +		TRANSPORT_##name = BIT(__COUNTER__ - TRANSPORT_COUNTER_BASE),
>
> WARNING: Argument 'symbol' is not used in function-like macro
> #114: FILE: tools/testing/vsock/util.h:20:
> +	#define _(name, symbol)	\
> +		TRANSPORT_##name = BIT(__COUNTER__ - TRANSPORT_COUNTER_BASE),
>
> WARNING: Argument 'name' is not used in function-like macro
> #122: FILE: tools/testing/vsock/util.h:28:
> +	#define _(name, symbol) "d " symbol "_transport",
>
> Is it ok to ignore this? FWIW, I see the same ERRORs due to similarly used
> preprocessor directives in fs/bcachefs/alloc_background_format.h, and the
> same WARNINGs about unused macro arguments in arch/x86/include/asm/asm.h
> (e.g. __ASM_SEL).

It's just test, so I think it's fine to ignore, but please exaplain it 
in the commit description with also references to other ERRORs/WARNINGs 
like you did here. Let's see what net maintainers think.

Thanks,
Stefano