Hi Dejin,

Thank you for all the work here!

The subject and the commit message could be improved to include a little
more details about why do you want to do it, and what problems does it
aims to solve.

Introduce pcim_alloc_irq_vectors(), a explicit device-managed version of
pci_alloc_irq_vectors().

You can probably drop the "explicit" word from the sentence above.
 

+/**
+ * pcim_alloc_irq_vectors - a device-managed pci_alloc_irq_vectors()
+ *
+ * It depends on calling pcim_enable_device() to make irq resources manageable.
+ */

It would be "IRQ" in the sentence above.  Also see [1] for more details
about how to make a patch ready to be accepted.

Also, this comment looks like it's intended to be compliant with the
kernel-doc format, and if so, then you should describe each argument as
the bare minimum, so that the entire comment would become this function
documentation making it also a little more useful.  See [2] for an
example of how to use kernel-doc.

+int pcim_alloc_irq_vectors(struct pci_dev *dev, unsigned int min_vecs,
+				unsigned int max_vecs, unsigned int flags)
+{
+	struct pci_devres *dr;
+
+       /*Ensure that the pcim_enable_device() function has been called*/

The comment above has to be correctly aligned and it's also missing
spaces around the sentence to be properly formatted, see [3].

+	dr = find_pci_dr(dev);
+	if (!dr || !dr->enabled)
+		return -EINVAL;
+
+	return pci_alloc_irq_vectors(dev, min_vecs, max_vecs, flags);
+}

Question: wouldn't you need to call pci_free_irq_vectors() somewhere,
possibly to pcim_release() callback?  Although, I am not sure where the
right place would be.

I am asking, as the documentation (see [4]) suggests that one would have
to release allocated IRQ vectors (relevant exceprt):

quoted

To automatically use MSI or MSI-X interrupt vectors, use the following
function:

 int pci_alloc_irq_vectors(struct pci_dev *dev, unsigned int min_vecs,
	unsigned int max_vecs, unsigned int flags);

which allocates up to max_vecs interrupt vectors for a PCI device.

(...)

Any allocated resources should be freed before removing the device using
the following function:

 void pci_free_irq_vectors(struct pci_dev *dev);

What do you think?

1. https://lore.kernel.org/linux-pci/20171026223701.GA25649@bhelgaas-glaptop.roam.corp.google.com/ (local)
2. https://www.kernel.org/doc/html/latest/doc-guide/kernel-doc.html
3. https://www.kernel.org/doc/html/latest/process/coding-style.html
4. https://www.kernel.org/doc/html/latest/PCI/msi-howto.html

Krzysztof