Re: [RFC v2 3/8] xen/arm: Export host device-tree to hypfs

[Julien Grall <julien@xxxxxxx>]

Hi,

On 09/02/2022 18:51, Oleksii Moisieiev wrote:
> On Wed, Feb 09, 2022 at 12:17:17PM +0000, Julien Grall wrote:
> > > > > +static HYPFS_DIR_INIT_FUNC(host_dt_dir, HOST_DT_DIR, &host_dt_dir_funcs);
> > > > > +
> > > > > +static int __init host_dtb_export_init(void)
> > > > > +{
> > > > > +    ASSERT(dt_host && (dt_host->sibling == NULL));
> > > > dt_host can be NULL when booting on ACPI platform. So I think this wants to
> > > > be turned to a normal check and return directly.
> > > I will replace if with
> > > if ( !acpi_disabled )
> > >       return -ENODEV;
> > >
> > > > Also could you explain why you need to check dt_host->sibling?
> > > This is my way to check if dt_host points to the top of the device-tree.
> > > In any case I will replace it with !acpi_disabled as I mentioned
> > > earlier.
> > dt_host will always points to the root of the host device-tree. I don't
> > think it is the job of hypfs to enforce it unless you expect the code to be
> > buggy if this happens. But then I would argue the code should be hardened.
> Hi Julien,
>
> Unfortunatelly I can't use acpi_disabled in host_dtb_export_init because
> I've already moved host_dtb_export.c to the common folder.
I am sorry, but I don't understand why moving the code to common code 
prevents you to use !acpi_disabled. Can you clarify?
> As for the host->sibling - I took the whole assert:
> ASSERT(dt_host && (dt_host->sibling == NULL));
> from the prepare_dtb_hwdom function. And this assertion was added by the
> commit b8f1c5e7039efbe1103ed3fe4caedf8c34affe13 authored by you.
I am not sure what's your point... Yes I wrote the same ASSERT() 9 years 
time. But people view evolves over the time.
There are some code I wished I had written differently (How about you? 
;)). However, I don't have the time to rewrite everything I ever wrote. 
That said, I can at least make sure they are not spread.
> What do you think if I omit dt_host->sibling check and make it:
>
> if ( !dt_host )
>      return -ENODEV;
We used to set dt_host even when booting with ACPI but that shouldn't be 
the case anymore. So I think this check should be fine.
Cheers,

--
Julien Grall