Re: [PATCH v5 3/4] PCI: endpoint: Add support for DOE initialization and setup in EPC core

[Aksh Garg]

On 12/06/26 00:42, Bjorn Helgaas wrote:
> On Wed, Jun 10, 2026 at 03:32:55PM +0530, Aksh Garg wrote:
> > Add pci_epc_init_capabilities() in EPC core driver to initialize and
> > setup the capabilities supported by the EPC driver. This calls
> > pci_epc_doe_setup() to setup the DOE framework for an endpoint controller,
> > which discovers the DOE capabilities (extended capability ID 0x2E), and
> > registers each discovered DOE mailbox for all the functions in the
> > endpoint controller.
> >
> > Add pci_epc_deinit_capabilities() in EPC core driver for cleanup of the
> > resources used by the capabilities of the EPC driver. This calls
> > pci_ep_doe_destroy() to destroy all DOE mailboxes and free associated
> > resources.
> >
> > Co-developed-by: Siddharth Vadapalli <s-vadapalli@xxxxxx>
> > Signed-off-by: Siddharth Vadapalli <s-vadapalli@xxxxxx>
> > Signed-off-by: Aksh Garg <a-garg7@xxxxxx>
> > ---
> > +/**
> > + * pci_epc_doe_setup() - Discover and setup DOE mailboxes for all functions
> > + * @epc: the EPC device on which DOE mailboxes has to be setup
> > + *
> > + * Discover DOE (Data Object Exchange) capabilities for all physical functions
> > + * in the endpoint controller and register DOE mailboxes.
> > + *
> > + * Returns: 0 on success, -errno on failure
> > + */
> > +static int pci_epc_doe_setup(struct pci_epc *epc)
> > +{
> > +	u8 func_no, vfunc_no = 0;
> > +	u16 cap_offset;
> > +	int ret;
> > +
> > +	if (!epc->ops || !epc->ops->find_ext_capability)
> > +		return -EINVAL;

Hi Bjorn,

Thank you for your feedback comments. I will work on them and post v6
series incorporating the changes.

> I don't see anything that sets pci_epc_ops.find_ext_capability in this
> series, so this looks currently unused and untestable, so likely not
> mergeable as-is.  What's the plan for users of this?

Currently there is no EPC driver upstream which supports DOE yet. 
However, I am working on a platform which supports DOE (support for
which would be added soon). Mani pointed out that if EPC driver support
for the same is guaranteed to be added soon, the APIs can be merged
first.

For the demonstration purpose, he asked to show how an EPC driver is
expected to use the API as a snippet in the cover letter itself.

I will add a code snippet in the cover letter, which sets
pci_epc_ops.find_ext_capability as well, if that is acceptable.

Regards,
Aksh Garg

> > +	/* Discover DOE capabilities for all functions */
> > +	for (func_no = 0; func_no < epc->max_functions; func_no++) {
> > +		mutex_lock(&epc->lock);
> > +		cap_offset = epc->ops->find_ext_capability(epc, func_no,
> > +							   vfunc_no, 0,
> > +							   PCI_EXT_CAP_ID_DOE);
> > +		mutex_unlock(&epc->lock);
> > +
> > +		while (cap_offset) {
> > +			/* Register this DOE mailbox */
> > +			ret = pci_ep_doe_add_mailbox(epc, func_no, cap_offset);
> > +			if (ret) {
> > +				dev_warn(&epc->dev,
> > +					 "[pf%d:offset %x] failed to add DOE mailbox\n",
> > +					 func_no, cap_offset);
> > +			}
> > +
> > +			mutex_lock(&epc->lock);
> > +			cap_offset = epc->ops->find_ext_capability(epc, func_no,
> > +								   vfunc_no, cap_offset,
> > +								   PCI_EXT_CAP_ID_DOE);
> > +			mutex_unlock(&epc->lock);
> > +		}
> > +	}
> > +
> > +	dev_dbg(&epc->dev, "DOE mailboxes setup complete\n");
> > +	return 0;
> > +}
> > +