Re: [PATCH RFC 3/3] net: vertexcom: Add MSE102x SPI support

On Thu, Sep 16, 2021 at 02:35:41PM +0200, Andrew Lunn wrote:

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+	netif_carrier_off(mse->ndev);
+	ndev->if_port = IF_PORT_10BASET;

That is not correct. Maybe you should add a IF_PORT_HOMEPLUG ?

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There is already a driver (qca_spi, qcauart) for a similiar Homeplug
device (QCA7000), which also uses IF_PORT_10BASET. Should i change this
too or leave it because of resulting changes to userspace?

Technically, it would be an ABI change. But ifmap seems pretty loosely
defined. See man 7 netdevice:

       SIOCGIFMAP, SIOCSIFMAP
              Get or set the interface's hardware parameters using ifr_map.
	      Setting the parameters is a privileged operation.

                  struct ifmap {
                      unsigned long   mem_start;
                      unsigned long   mem_end;
                      unsigned short  base_addr;
                      unsigned char   irq;
                      unsigned char   dma;
                      unsigned char   port;
                  };

              The interpretation of the ifmap structure depends on the device driver
	      and the architecture.

The if_port value ends up in port. And i've no idea where it is
actually available in user space. iproute2 does not use it, nor
ethtool. So, i would say, submit a separate patch for the other
drivers, and we will see if anybody notices.

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+static const struct of_device_id mse102x_match_table[] = {
+	{ .compatible = "vertexcom,mse1021" },
+	{ .compatible = "vertexcom,mse1022" },

Is there an ID register you can read to determine what device you
actually have? If so, i suggest you verify the correct compatible is
used.

AFAIK the device doesn't have any kind of ID register.

Then i would suggest changing the compatible to "vertexcom,mse102x".

Don't use wildcards in compatible strings.

If you cannot verify it, and it makes no actual difference, then 50%
of the boards will use the wrong one. Which means you can then later
not actually make use of it to enable features specific to a
compatible string.

A wildcard doesn't help with this. If some boards are wrong, not any way 
we can fix that short of a DT update. If you can update the DT, then you 
can correct the string then.

Rob