Re: [Qemu-devel] [PATCHv9 3/3] fw_cfg: move QOM type defines and fw_cfg types into fw_cfg.h

[Eduardo Habkost <ehabkost@redhat.com>]

On Sun, Jul 16, 2017 at 08:12:13PM +0100, Mark Cave-Ayland wrote:
> On 14/07/17 19:56, Eduardo Habkost wrote:
> 
> >>> Why do you need the full struct declaration to be exposed in the
> >>> header?
> >>
> >> Different board code wants to hook up "comb_iomem" manually to different
> >> address spaces, so they need to access the field directly. This is the
> >> ultimate goal of the entire exercise, IIRC.
> 
> Yes, that is correct (and I believe is mentioned in the cover letter, too).
> 
> >>> The memory regions are supposed to be visible as QOM
> >>> children to the fw_cfg device, already.
> >>
> >> I don't understand this. How else can board code work with "comb_iomem"
> >> than described above? If there is a way, I agree it would be preferable.
> > 
> > object_resolve_path_component(fw_cfg, "fwcfg[0]") and
> > object_resolve_path_component(fw_cfg, "fwcfg.dma[0]") should
> > return fw_cfg->comb_iomem and fw_cfg->dma_iomem, respectively.
> > 
> > I don't know why those names were chosen, though.  Probably it's
> > a good idea to call object_property_add_child() manually with
> > more appropriate names inside the fw_cfg code instead of letting
> > memory_region_init() pick the child name.
> 
> That's interesting. I did a grep of the codebase for
> object_resolve_path_component and struggled to find an instance where it
> was being used to provide access to a MemoryRegion. Even if it's an
> available feature, it's certainly not one that is widely known about.
> 
> In terms of the patch, is the v9 revision suitable for commit or does
> this constitute a NACK?

It's not a NACK.  Using QOM properties instead of direct struct
access may be nice (I'm not 100% sure, either), but not required.

-- 
Eduardo