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

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Date:   Mon, 1 Feb 2021 09:50:41 -0800
From:   Ben Widawsky <ben.widawsky@...el.com>
To:     Konrad Rzeszutek Wilk <konrad.wilk@...cle.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

On 21-02-01 12:41:36, Konrad Rzeszutek Wilk wrote:
> > +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' ?
> 

Funny that.
https://lore.kernel.org/linux-cxl/20201111073449.GA16235@infradead.org/

> > +			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?
> 

I'm not following the request. CXL_GET_FIELD is just doing the shift and mask on
cap.

Can you explain what you're hoping to see?

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