Re: [igt-dev] [PATCH v3 2/3] lib: implement new engine discovery interface

[Andi Shyti <andi.shyti@intel.com>]

Hi Tvrtko,

> > +	ctx_param.ctx_id = ctx_id;
> > +	ctx_param.size = size;
> > +	ctx_param.param = I915_CONTEXT_PARAM_ENGINES;
> > +	ctx_param.value = to_user_pointer(ctx_engine);
> > +
> > +	/* check whether we free the engines */
> > +	igt_require(!ioctl(fd, DRM_IOCTL_I915_GEM_CONTEXT_SETPARAM, &ctx_param));
> > +
> > +	free(ctx_engine);
> 
> Leaks on skip, not that it matters a lot, but the comments makes me think
> you wanted to handle it.

The comment is a leftover from the cleanup. I need to fix/remove
it.

While as for freeing ctx_engine in case of failure, some ugly code
would be required. I think it's cleaner to leave it as it is,
anyway 'igt_require' exits in case of failure.

> > +#define for_each_engine_ctx(fd, ctx, e) \
> > +		for (int __m = __gem_setup_ctx_engines(fd, ctx), __e = e = 1; \
> > +				__e <= __m; e = ++__e)
> > +
> 
> Is __e needed? Could just use passed in e?

I cannot mix declarations and "already declared variables"
initializations in the first expression in 'for'. If I do
something like:

  for (int __m = __gem_setup_ctx_engines(), e = 1; ... )

I would re-define 'e' and it would be a different variable
outside the loop.

So that either I declare '__m' outside, or I initialize 'e'
outside, or I use the double 'for' loop as it was done
previously, or do some ugly tricks.

It looked simplier to define an '__e'.

Am I missing anything?

> >   bool gem_ring_is_physical_engine(int fd, unsigned int ring);
> >   bool gem_ring_has_physical_engine(int fd, unsigned int ring);
> > +int __gem_setup_ctx_engines(int fd, uint32_t ctx_id);
> >   bool gem_can_store_dword(int fd, unsigned int engine);
> > 
> 
> Looks okay. But we need to decide whether we want the iterator to be a
> struct sooner rather than later now.
> 
> I think if you go and convert one of the tests which uses
> for_each_physical_engine to enumerate subtests and so, it will become
> clearer what approach work better. (struct iterator, or helpers to get data
> from engine index.)

All right, I'll try it out and I will post something as a reply to this
patch.

Thanks a lot, Tvrtko!
Andi
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