Subject: Re: [PATCH v9 2/3] of: factor arguments passed to of_map_id() into a struct

From: Marc Zyngier <[email-masked]>
Date: Sun, 01 Mar 2026 11:45:12 +0000

On Sun, 01 Mar 2026 10:59:23 +0000,
Dmitry Baryshkov <[email-masked]> wrote:
> 
> On Sun, Mar 01, 2026 at 02:04:20PM +0530, Vijayanand Jitta wrote:
> > From: Charan Teja Kalla <[email-masked]>
> > 
> > Change of_map_id() to take a pointer to struct of_phandle_args
> > instead of passing target device node and translated IDs separately.
> > Update all callers accordingly.
> > 
> > Subsequent patch will make use of the args_count field in
> > struct of_phandle_args.
> > 
> > Suggested-by: Rob Herring (Arm) <[email-masked]>
> > Signed-off-by: Charan Teja Kalla <[email-masked]>
> > Signed-off-by: Vijayanand Jitta <[email-masked]>
> > ---
> >  drivers/iommu/of_iommu.c              |  2 +-
> >  drivers/of/base.c                     | 37 +++++++++++++++++------------------
> >  drivers/pci/controller/dwc/pci-imx6.c |  8 +++++++-
> >  drivers/pci/controller/pcie-apple.c   |  4 +++-
> >  drivers/xen/grant-dma-ops.c           |  2 +-
> >  include/linux/of.h                    | 21 +++++++++++++-------
> >  6 files changed, 44 insertions(+), 30 deletions(-)
> > 
> > diff --git a/drivers/pci/controller/pcie-apple.c b/drivers/pci/controller/pcie-apple.c
> > index a0937b7b3c4d..e1d4b37d200d 100644
> > --- a/drivers/pci/controller/pcie-apple.c
> > +++ b/drivers/pci/controller/pcie-apple.c
> > @@ -755,6 +755,7 @@ static int apple_pcie_enable_device(struct pci_host_bridge *bridge, struct pci_d
> >  {
> >  	u32 sid, rid = pci_dev_id(pdev);
> >  	struct apple_pcie_port *port;
> > +	struct of_phandle_args iommu_spec = { .args_count = 1 };
> 
> Hmm, I didn't notice this. Parsing functions are expected to ignore
> of_phandle_args before the parsing. So passing .args_count = 1 is
> strange.

It isn't strange. It is a semantic requirement. It explicitly
indicates the boundary of what the driver is prepared to receive, just
like passing a single u32 * is perfectly clear.

Frankly, this patch makes an absolute mess of the current API.

	M.

-- 
Without deviation from the norm, progress is not possible.