Re: [PATCH net-next 07/15] mfd: core: add ability for cells to probe on a custom parent OF node

Lee Jones
2025-11-20T14:41:41Z

On Tue, 18 Nov 2025, Vladimir Oltean wrote:

> I would like the "nxp,sja1110a" driver, in the configuration below, to
> be able to probe the drivers for "nxp,sja1110-base-t1-mdio" and for
> "nxp,sja1110-base-tx-mdio" via mfd_add_devices():
>
> ethernet-switch@0 {
> compatible = "nxp,sja1110a";
>
> mdios {
> mdio@0 {
> compatible = "nxp,sja1110-base-t1-mdio";
> };
>
> mdio@1 {
> compatible = "nxp,sja1110-base-tx-mdio";
> };
> };
> };

This device is not an MFD.

Please find a different way to instantiate these network drivers.

> This isn't currently possible, because mfd assumes that the parent
> OF node ("mdios") == OF node of the parent ("ethernet-switch@0"), which
> in this case isn't true, and as it searches through the children of
> "ethernet-switch@0", it finds no MDIO bus to probe.
>
> Cc: Lee Jones <lee@kernel.org>
> Signed-off-by: Vladimir Oltean <vladimir.oltean@nxp.com>
> ---
> drivers/mfd/mfd-core.c | 11 +++++++++--
> include/linux/mfd/core.h | 7 +++++++
> 2 files changed, 16 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/mfd/mfd-core.c b/drivers/mfd/mfd-core.c
> index 7d14a1e7631e..e0b7f93a2654 100644
> --- a/drivers/mfd/mfd-core.c
> +++ b/drivers/mfd/mfd-core.c
> @@ -181,8 +181,14 @@ static int mfd_add_device(struct device *parent, int id,
> if (ret < 0)
> goto fail_res;
>
> - if (IS_ENABLED(CONFIG_OF) && parent->of_node && cell->of_compatible) {
> - for_each_child_of_node(parent->of_node, np) {
> + if (IS_ENABLED(CONFIG_OF)) {
> + const struct device_node *parent_of_node;
> +
> + parent_of_node = cell->parent_of_node ?: parent->of_node;
> + if (!parent_of_node || !cell->of_compatible)
> + goto skip_of;
> +
> + for_each_child_of_node(parent_of_node, np) {
> if (of_device_is_compatible(np, cell->of_compatible)) {
> /* Skip 'disabled' devices */
> if (!of_device_is_available(np)) {
> @@ -213,6 +219,7 @@ static int mfd_add_device(struct device *parent, int id,
> cell->name, platform_id);
> }
>
> +skip_of:
> mfd_acpi_add_device(cell, pdev);
>
> if (cell->pdata_size) {
> diff --git a/include/linux/mfd/core.h b/include/linux/mfd/core.h
> index faeea7abd688..2e94ea376125 100644
> --- a/include/linux/mfd/core.h
> +++ b/include/linux/mfd/core.h
> @@ -81,6 +81,13 @@ struct mfd_cell {
> /* Software node for the device. */
> const struct software_node *swnode;
>
> + /*
> + * Parent OF node of the device, if different from the OF node
> + * of the MFD parent (e.g. there is at least one more hierarchical
> + * level between them)
> + */
> + const struct device_node *parent_of_node;
> +
> /*
> * Device Tree compatible string
> * See: Documentation/devicetree/usage-model.rst Chapter 2.2 for details
> --
> 2.34.1
>

--
Lee Jones [李琼斯]