linux-kernel - Re: [PATCH 03/14] cxl/mem: Find device capabilities

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Message-ID: <20210201174136.GF197521@fedora>
Date:   Mon, 1 Feb 2021 12:41:36 -0500
From:   Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>
To:     Ben Widawsky <ben.widawsky@...el.com>
Cc:     linux-cxl@...r.kernel.org, linux-acpi@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux-nvdimm@...ts.01.org,
        linux-pci@...r.kernel.org, Bjorn Helgaas <helgaas@...nel.org>,
        Chris Browy <cbrowy@...ry-design.com>,
        Christoph Hellwig <hch@...radead.org>,
        Dan Williams <dan.j.williams@...el.com>,
        Ira Weiny <ira.weiny@...el.com>,
        Jon Masters <jcm@...masters.org>,
        Jonathan Cameron <Jonathan.Cameron@...wei.com>,
        Rafael Wysocki <rafael.j.wysocki@...el.com>,
        Randy Dunlap <rdunlap@...radead.org>,
        Vishal Verma <vishal.l.verma@...el.com>,
        daniel.lll@...baba-inc.com,
        "John Groves (jgroves)" <jgroves@...ron.com>,
        "Kelley, Sean V" <sean.v.kelley@...el.com>
Subject: Re: [PATCH 03/14] cxl/mem: Find device capabilities

> +static int cxl_mem_setup_regs(struct cxl_mem *cxlm)
> +{
> +	struct device *dev = &cxlm->pdev->dev;
> +	int cap, cap_count;
> +	u64 cap_array;
> +
> +	cap_array = readq(cxlm->regs + CXLDEV_CAP_ARRAY_OFFSET);
> +	if (CXL_GET_FIELD(cap_array, CXLDEV_CAP_ARRAY_ID) != CXLDEV_CAP_ARRAY_CAP_ID)
> +		return -ENODEV;
> +
> +	cap_count = CXL_GET_FIELD(cap_array, CXLDEV_CAP_ARRAY_COUNT);
> +
> +	for (cap = 1; cap <= cap_count; cap++) {
> +		void __iomem *register_block;
> +		u32 offset;
> +		u16 cap_id;
> +
> +		cap_id = readl(cxlm->regs + cap * 0x10) & 0xffff;
> +		offset = readl(cxlm->regs + cap * 0x10 + 0x4);
> +		register_block = cxlm->regs + offset;
> +
> +		switch (cap_id) {
> +		case CXLDEV_CAP_CAP_ID_DEVICE_STATUS:
> +			dev_dbg(dev, "found Status capability (0x%x)\n",
> +				offset);

That 80 character limit is no longer a requirement. Can you just make
this one line? And perhaps change 'found' to 'Found' ?

> +			cxlm->status.regs = register_block;
> +			break;
> +		case CXLDEV_CAP_CAP_ID_PRIMARY_MAILBOX:
> +			dev_dbg(dev, "found Mailbox capability (0x%x)\n",
> +				offset);
> +			cxlm->mbox.regs = register_block;
> +			break;
> +		case CXLDEV_CAP_CAP_ID_SECONDARY_MAILBOX:
> +			dev_dbg(dev,
> +				"found Secondary Mailbox capability (0x%x)\n",
> +				offset);
> +			break;
> +		case CXLDEV_CAP_CAP_ID_MEMDEV:
> +			dev_dbg(dev, "found Memory Device capability (0x%x)\n",
> +				offset);
> +			cxlm->mem.regs = register_block;
> +			break;
> +		default:
> +			dev_warn(dev, "Unknown cap ID: %d (0x%x)\n", cap_id,
> +				 offset);
> +			break;
> +		}
> +	}
> +
> +	if (!cxlm->status.regs || !cxlm->mbox.regs || !cxlm->mem.regs) {
> +		dev_err(dev, "registers not found: %s%s%s\n",
> +			!cxlm->status.regs ? "status " : "",
> +			!cxlm->mbox.regs ? "mbox " : "",
> +			!cxlm->mem.regs ? "mem" : "");
> +		return -ENXIO;
> +	}
> +
> +	return 0;
> +}
> +
> +static int cxl_mem_setup_mailbox(struct cxl_mem *cxlm)
> +{
> +	const int cap = cxl_read_mbox_reg32(cxlm, CXLDEV_MB_CAPS_OFFSET);
> +
> +	cxlm->mbox.payload_size =
> +		1 << CXL_GET_FIELD(cap, CXLDEV_MB_CAP_PAYLOAD_SIZE);
> +

I think the static analyzers are not going to be happy that you are not
checking the value of `cap` before using it.

Perhaps you should check that first before doing the manipulations?

> +	/* 8.2.8.4.3 */
> +	if (cxlm->mbox.payload_size < 256) {

#define for 256?