Re: [RFC PATCH] software node: Skip duplicated software_node sysfs

[Rafael J. Wysocki]

On Tue, Nov 16, 2021 at 4:54 AM Qian Cai <quic_qiancai@xxxxxxxxxxx> wrote:
>
> On Fri, Nov 05, 2021 at 09:39:42PM +0200, Andy Shevchenko wrote:
> > > Anyway, what's the "upper layer"? Is that "struct device" or "struct
> > > swnode"? I suppose you meant:
> >
> > struct device here.
> >
> > > - Remove "secondary" field from "struct fwnode_handle".
> > > - Replace "fwnode" from "upper layer" with
> > >   "struct list_head fwnode_head;".
> > > - Modify all functions in "software_node_ops" to use "fwnode_head".
> > >
> > > Is that correct?
> >
> > Yes.
> >
> > It might be a bit complicated taking into account how much fwnode is
> > spreaded in the kernel... Basically, you need to fix all direct
> > accesses to the dev->fwnode first.
> > Besides that you need to check that fwnode, which is used out of the
> > device scope, like in IRQ domains, doesn't use secondary pointer(s).
> >
> > This nevertheless adds a lot of flexibility and we may add whatever
> > type of fwnodes and mix them together.
>
> Okay, here is my plan until someone still has an idea to avoid a
> redesign.
>
> Frist, fixes all dev->fwnode / dev.fwnode to use dev_fwnode(). This
> could be a standalone tree-wide patchset going out to avoid
> heavy-lifting later.
>
> Then, we can create another patchset on top. I have audited
> "irq_domain" but not seen any "secondary" leakage. Struct
> "cht_int33fe_data" does have some need to fix.
>
> Rename set_secondary_fwnode() to insert_secondary_fwnode(). Fix things
> in drivers/base/core.c, swnode.c etc to use the new fwnode_head and
> anything I can't think of right now.
>
> Since we will have multiple "software_node" (secondary fwnode:s) for a
> single "device". What would be the usual way to deal with a
> linked-list in the sysfs? I can think of just let "software_node"
> become a directory to host a list of symlinks named from
> swnode->id. Thoughts?

Note that one pointer dereference in ACPI_COMPANION() is enough.