[PATCH v6 24/31] of/irq: Add of_msi_xlate() helper function

[Lorenzo Pieralisi]

On Fri, Jun 27, 2025 at 04:32:41PM -0500, Rob Herring wrote:
> On Thu, Jun 26, 2025 at 12:26:15PM +0200, Lorenzo Pieralisi wrote:
> > Add an of_msi_xlate() helper that maps a device ID and returns
> > the device node of the MSI controller the device ID is mapped to.
> > 
> > Required by core functions that need an MSI controller device node
> > pointer at the same time as a mapped device ID, of_msi_map_id() is not
> > sufficient for that purpose.
> > 
> > Signed-off-by: Lorenzo Pieralisi <lpieralisi at kernel.org>
> > Cc: Rob Herring <robh at kernel.org>
> > Cc: Marc Zyngier <maz at kernel.org>
> > ---
> >  drivers/of/irq.c       | 22 +++++++++++++++++-----
> >  include/linux/of_irq.h |  5 +++++
> >  2 files changed, 22 insertions(+), 5 deletions(-)
> > 
> > diff --git a/drivers/of/irq.c b/drivers/of/irq.c
> > index f8ad79b9b1c9..74aaea61de13 100644
> > --- a/drivers/of/irq.c
> > +++ b/drivers/of/irq.c
> > @@ -670,8 +670,20 @@ void __init of_irq_init(const struct of_device_id *matches)
> >  	}
> >  }
> >  
> > -static u32 __of_msi_map_id(struct device *dev, struct device_node **np,
> > -			    u32 id_in)
> > +/**
> > + * of_msi_xlate - map a MSI ID and find relevant MSI controller node
> > + * @dev: device for which the mapping is to be done.
> > + * @msi_np: Pointer to store the MSI controller node
> > + * @id_in: Device ID.
> > + *
> > + * Walk up the device hierarchy looking for devices with a "msi-map"
> > + * property. If found, apply the mapping to @id_in. @msi_np pointed
> > + * value must be NULL on entry, if an MSI controller is found @msi_np is
> > + * initialized to the MSI controller node with a reference held.
> > + *
> > + * Returns: The mapped MSI id.
> > + */
> > +u32 of_msi_xlate(struct device *dev, struct device_node **msi_np, u32 id_in)
> >  {
> >  	struct device *parent_dev;
> >  	u32 id_out = id_in;
> > @@ -682,7 +694,7 @@ static u32 __of_msi_map_id(struct device *dev, struct device_node **np,
> >  	 */
> >  	for (parent_dev = dev; parent_dev; parent_dev = parent_dev->parent)
> >  		if (!of_map_id(parent_dev->of_node, id_in, "msi-map",
> > -				"msi-map-mask", np, &id_out))
> > +				"msi-map-mask", msi_np, &id_out))
> >  			break;
> >  	return id_out;
> >  }
> > @@ -700,7 +712,7 @@ static u32 __of_msi_map_id(struct device *dev, struct device_node **np,
> >   */
> >  u32 of_msi_map_id(struct device *dev, struct device_node *msi_np, u32 id_in)
> 
> Can we replace the 2 callers of of_msi_map_id() with of_msi_xlate()? 

Yes we could - with a separate patch, it is a clean-up (current
of_msi_map_id() users call it with a specific of_node target, I did not
convert it in *this* patch to prevent adding issues - I will also add
relevant kdoc info related to the of_node parameter in of_msi_xlate()
that will need to be changed).

> The series is already big enough, so that can be a follow-up or do it 
> for 6.17 if the series isn't going to make it.

I will put together a patch - I don't think it belongs in this series
but depending on whether I need to do a v7 I will see what's best.

Thanks,
Lorenzo