Re: [PATCH v21 08/13] mfd: core: Add firmware-node support to MFD cells

[Shivendra Pratap]

On 28-04-2026 18:33, Shivendra Pratap wrote:
> On 28-04-2026 18:21, Bartosz Golaszewski wrote:
> > On Tue, Apr 28, 2026 at 2:18 PM Shivendra Pratap
> > <shivendra.pratap@xxxxxxxxxxxxxxxx> wrote:
> > > On 28-04-2026 13:33, Bartosz Golaszewski wrote:
> > > > On Mon, 27 Apr 2026 19:34:48 +0200, Shivendra Pratap
> > > > <shivendra.pratap@xxxxxxxxxxxxxxxx> said:
> > > > > MFD core has no way to register a child device using an explicit 
> > > > > firmware
> > > > > node. This prevents drivers from registering child nodes when those 
> > > > > nodes
> > > > > do not define a compatible string. One such example is the PSCI
> > > > > "reboot-mode" node, which omits a compatible string as it describes
> > > > > boot-states provided by the underlying firmware.
> > > > >
> > > > > Extend struct mfd_cell with an optional fwnode pointer and attach 
> > > > > it to the
> > > > > child device during registration when no firmware node is already 
> > > > > assigned.
> > > > >
> > > > > Signed-off-by: Shivendra Pratap <shivendra.pratap@xxxxxxxxxxxxxxxx>
> > > > > ---
> > > >
> > > > In the following patch you use this and violate the supposed 
> > > > constness of
> > > > MFD cells. This also mean you need to modify the mfd_cell at run- 
> > > > time. I would
> > > > prefer introducing a field in mfd_cell: bool use_parent_fwnode which 
> > > > would
> > > > indicate to MFD core that - in case no fwnode was assigned from 
> > > > other sources:
> > > > DT or software node - it should reuse the parent MFD device's node.
> > >
> > > Have one doubt on this, When we fallback to use_parent_fwnode for cell:
> > > psci-reboot-mode, at psci_reboot_mode_probe(), pDev->dev->of_node point
> > > to psci node.
> > >
> > > But we want dev->of_node to point to "reboot-mode" node. This may need
> > > an explicit assignment again of of_node?
> >
> > Ah, sorry you're right. I'd like to avoid having to modify the
> > mfd_cell entry at run-time if possible.
> >
> > How about a callback in mfd_cell like:
> >
> > struct fwnode_handle *(*get_fwnode)(struct device *parent);
> >
> > If set, it would be called from MFD core and would do the name lookup
> > and return the fwnode which would then be assigned to the cell device?

Or should we just drop this patch for fwnode in mfd-core?

Export a new call in reboot-mode framework as:
reboot_mode_register_node(struct reboot_mode_driver *reboot, 
                  struct device_node *np / fwnode)

Use the parent node in psci-reboot-mode and find reboot-mode and call 
reboot_mode_register_node?

thanks,
Shivendra

> sure. thanks. We can make it a callback from MFD core.
>
> thanks,
> Shivendra