linux-kernel - Re: [PATCH V12 3/9] PCI: Create PCIe library functions in support of DOE mailboxes.

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Date:   Tue, 28 Jun 2022 15:38:48 +0100
From:   Jonathan Cameron <Jonathan.Cameron@...wei.com>
To:     <ira.weiny@...el.com>
CC:     Dan Williams <dan.j.williams@...el.com>,
        Bjorn Helgaas <bhelgaas@...gle.com>,
        "Li, Ming" <ming4.li@...el.com>,
        Bjorn Helgaas <helgaas@...nel.org>,
        Lukas Wunner <lukas@...ner.de>,
        Alison Schofield <alison.schofield@...el.com>,
        Vishal Verma <vishal.l.verma@...el.com>,
        "Dave Jiang" <dave.jiang@...el.com>,
        Ben Widawsky <bwidawsk@...nel.org>,
        <linux-kernel@...r.kernel.org>, <linux-cxl@...r.kernel.org>,
        <linux-pci@...r.kernel.org>
Subject: Re: [PATCH V12 3/9] PCI: Create PCIe library functions in support
 of DOE mailboxes.

On Mon, 27 Jun 2022 21:15:21 -0700
ira.weiny@...el.com wrote:

> From: Jonathan Cameron <Jonathan.Cameron@...wei.com>
> 
> Introduced in a PCIe r6.0, sec 6.30, DOE provides a config space based
> mailbox with standard protocol discovery.  Each mailbox is accessed
> through a DOE Extended Capability.
> 
> Each DOE mailbox must support the DOE discovery protocol in addition to
> any number of additional protocols.
> 
> Define core PCIe functionality to manage a single PCIe DOE mailbox at a
> defined config space offset.  Functionality includes iterating,
> creating, query of supported protocol, and task submission.  Destruction
> of the mailboxes is device managed.
> 
> If interrupts are desired, the interrupt number can be queried and
> passed to the create function.  Passing a negative value disables
> interrupts for that mailbox.  It is the caller's responsibility to ensure
> enough interrupt vectors are allocated.
> 
> Cc: "Li, Ming" <ming4.li@...el.com>
> Cc: Bjorn Helgaas <helgaas@...nel.org>
> Signed-off-by: Jonathan Cameron <Jonathan.Cameron@...wei.com>
> Co-developed-by: Ira Weiny <ira.weiny@...el.com>
> Signed-off-by: Ira Weiny <ira.weiny@...el.com>

+static void *pci_doe_xa_entry(u16 vid, u8 prot)
+{
+	return (void *)(((unsigned long)vid << 16) | prot);
+}
...

> +static int pci_doe_cache_protocols(struct pci_doe_mb *doe_mb)
> +{
> +	u8 index = 0;
> +	u8 xa_idx = 0;
> +
> +	do {
> +		int rc;
> +		u16 vid;
> +		u8 prot;
> +
> +		rc = pci_doe_discovery(doe_mb, &index, &vid, &prot);
> +		if (rc)
> +			return rc;
> +
> +		pci_dbg(doe_mb->pdev,
> +			"[%x] Found protocol %d vid: %x prot: %x\n",
> +			doe_mb->cap_offset, xa_idx, vid, prot);
> +
> +		rc = xa_insert(&doe_mb->prots, xa_idx++,
> +			       pci_doe_xa_entry(vid, prot), GFP_KERNEL);

I'm not that familiar with xarray, but the docs suggest that you have
to use xa_mk_value() to store an integer directly into it.

> +		if (rc)
> +			return -ENOMEM;
> +	} while (index);
> +
> +	return 0;
> +}
> +