linux-kernel - Re: [RFC PATCH] software node: Skip duplicated software

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Date:   Mon, 15 Nov 2021 22:54:54 -0500
From:   Qian Cai <quic_qiancai@...cinc.com>
To:     Andy Shevchenko <andy.shevchenko@...il.com>
CC:     "Rafael J. Wysocki" <rafael@...nel.org>,
        Andy Shevchenko <andriy.shevchenko@...ux.intel.com>,
        Heikki Krogerus <heikki.krogerus@...ux.intel.com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Laurentiu Tudor <laurentiu.tudor@....com>,
        "linux-acpi@...r.kernel.org" <linux-acpi@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [RFC PATCH] software node: Skip duplicated software_node sysfs

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?