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

[Shivendra Pratap <shivendra.pratap@oss.qualcomm.com>]

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@oss.qualcomm.com> wrote:
>>>
>>>
>>>
>>> On 28-04-2026 13:33, Bartosz Golaszewski wrote:
>>>> On Mon, 27 Apr 2026 19:34:48 +0200, Shivendra Pratap
>>>> <shivendra.pratap@oss.qualcomm.com> 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@oss.qualcomm.com>
>>>>> ---
>>>>
>>>> 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