回复：[PATCH v23 net-next 02/12] net/nebula-matrix: add core driver architecture and HW layer initializat ion

Review comments for V22
>On Thu, 23 Jul 2026 12:00:54 +0800 illusion.wang wrote:
>> + err = dma_set_mask_and_coherent(dev, DMA_BIT_MASK(64));
>> + if (err) {
>> +  dev_dbg(dev, "Configure DMA 64 bit mask failed, err = %d\n",
>> +   err);
>> +  dma_32_err = dma_set_mask_and_coherent(dev, DMA_BIT_MASK(32));
>> +  if (dma_32_err) {

>Read the documentation for the DMA API, dma_set_mask_and_coherent()
>is guaranteed to succeed in some cases..
As documented:
dma_set_mask_and_coherent() never return fail when DMA_BIT_MASK(64). Typical
error code like::

	/* Wrong code */
	if (dma_set_mask_and_coherent(dev, DMA_BIT_MASK(64)))
		dma_set_mask_and_coherent(dev, DMA_BIT_MASK(32))

dma_set_mask_and_coherent() will never return failure when bigger than 32.
So typical code like::

	/* Recommended code */
	if (support_64bit)
		dma_set_mask_and_coherent(dev, DMA_BIT_MASK(64));
	else
		dma_set_mask_and_coherent(dev, DMA_BIT_MASK(32));

Review comments for V23
>> +	err = dma_set_mask_and_coherent(dev, DMA_BIT_MASK(64));
>> +	if (err) {
>> +		dev_dbg(dev, "Configure DMA 64 bit mask failed, err = %d\n",
>> +			err);
>> +		dma_set_mask_and_coherent(dev, DMA_BIT_MASK(32));
>If the 64-bit mask configuration fails in nbl_probe(), and this 32-bit
>fallback also fails, does probe succeed anyway leaving the device with an
>unconfigured or invalid DMA mask?
>Since the return value of the fallback dma_set_mask_and_coherent() is
>ignored, the probe path will continue without a valid DMA mask configuration,
>which could cause subsequent DMA operations to fail or misbehave silently.
>> +	}
>> +	pci_set_master(pdev);
>> +
>> +	adapter = nbl_core_init(pdev, &param);

So My fix implementation is OK?
ret = dma_set_mask_and_coherent(&pdev->dev, DMA_BIT_MASK(64));
if (ret) {
	dev_err(&pdev->dev, "Set 64bit DMA mask failed %d, device cannot work\n", ret);
	goto err_out;
}
...
pci_set_master(pdev);
adapter = nbl_core_init(pdev, &param);