linux-kernel - Re: [PATCH v4 2/2] PCI: mediatek-gen3: Add support for restricting link width

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Message-ID: <20241104132046.GA2504924@rocinante>
Date: Mon, 4 Nov 2024 22:20:46 +0900
From: Krzysztof Wilczyński <kw@...ux.com>
To: AngeloGioacchino Del Regno <angelogioacchino.delregno@...labora.com>
Cc: linux-pci@...r.kernel.org, ryder.lee@...iatek.com,
	jianjun.wang@...iatek.com, lpieralisi@...nel.org, robh@...nel.org,
	bhelgaas@...gle.com, matthias.bgg@...il.com,
	linux-mediatek@...ts.infradead.org, linux-kernel@...r.kernel.org,
	linux-arm-kernel@...ts.infradead.org, kernel@...labora.com,
	fshao@...omium.org,
	Manivannan Sadhasivam <manivannan.sadhasivam@...aro.org>
Subject: Re: [PATCH v4 2/2] PCI: mediatek-gen3: Add support for restricting
 link width

Hello,

> +	ret = of_property_read_u32(dev->of_node, "num-lanes", &num_lanes);
> +	if (ret == 0) {
> +		if (num_lanes == 0 || num_lanes > 16 || (num_lanes != 1 && num_lanes % 2))
> +			dev_warn(dev, "Invalid num-lanes, using controller defaults\n");
> +		else
> +			pcie->num_lanes = num_lanes;
> +	}
> +
>  	return 0;
>  }

If you were to handle non-zero return value as an error here, perhaps the
property has not been set, then we could reduce the indentation here.

Something like this, perhaps?

  ret = of_property_read_u32(dev->of_node, "num-lanes", &num_lanes);
  if (ret) {
          dev_err(dev, "Failed to read num-lanes: %d\n", ret);
          return ret;
  }
  
  if (!num_lanes || num_lanes > 16 || (num_lanes != 1 && num_lanes % 2))
  	dev_warn(dev, "Invalid num-lanes, using controller defaults\n");
  else
  	pcie->num_lanes = num_lanes;

Does this make sense here?  Thoughts?

	Krzysztof