Re: [PATCH 2/2] of: net: fix of_get_mac_addr_nvmem() for PCI and DSA nodes

Am 2021-04-06 00:13, schrieb Andrew Lunn:

On Mon, Apr 05, 2021 at 11:46:04PM +0200, Michael Walle wrote:

quoted

Hi Andrew,

Am 2021-04-05 23:34, schrieb Andrew Lunn:

quoted

quoted

-static int of_get_mac_addr_nvmem(struct device_node *np, u8 addr)
+static int of_get_mac_addr_nvmem(struct device_node *np, u8 *addr)
 {
 	struct platform_device *pdev = of_find_device_by_node(np);
+	struct nvmem_cell *cell;
+	const void *mac;
+	size_t len;
 	int ret;

-	if (!pdev)
-		return -ENODEV;
+	/* Try lookup by device first, there might be a nvmem_cell_lookup
+	 * associated with a given device.
+	 */
+	if (pdev) {
+		ret = nvmem_get_mac_address(&pdev->dev, addr);
+		put_device(&pdev->dev);
+		return ret;
+	}

Can you think of any odd corner case where nvmem_get_mac_address()
would fail, but of_nvmem_cell_get(np, "mac-address") would work?

You mean, it might make sense to just return here when
nvmem_get_mac_address() will succeed and fall back to the
of_nvmem_cell_get() in case of an error?

I've not read the documentation for nvmem_get_mac_address(). I was
thinking we might want to return real errors, and -EPROBE_DEFER.

I can't follow, nvmem_get_mac_address() should already return those.

But maybe with -ENODEV we should try of_nvmem_cell_get()?

And if this happens - that is nvmem_get_mac_address(&pdev->dev) returns
-ENODEV - then of_nvmem_cell_get(np) will also return -ENODEV.

Because pdev->dev.of_node == np and nvmem_get_mac_address(&pdev->dev)
tries of_nvmem_cell_get(pdev->dev.of_node) first.

But i'm not sure if there are any real use cases? The only thing i can
think of is if np points to something deeper inside the device tree
than what pdev does?

But then pdev will be NULL and nvmem_get_mac_address() won't be called
at all, no?

-michael