fix some coding style problems

It has:
1. More newlines make the code block well separated.
2. Add more comments for msi_init.
3. Fix a indentation in vmxnet3.c.
4. ioh3420 & xio3130_downstream: put PCI Express capability init function
   together, make it more readable.

cc: Michael S. Tsirkin <mst@redhat.com>
cc: Markus Armbruster <armbru@redhat.com>
cc: Marcel Apfelbaum <marcel@redhat.com>
cc: Dmitry Fleytman <dmitry@daynix.com>
cc: Jason Wang <jasowang@redhat.com>

Reviewed-by: Markus Armbruster <armbru@redhat.com>
Reviewed-by: Marcel Apfelbaum <marcel@redhat.com>
Signed-off-by: Cao jin <caoj.fnst@cn.fujitsu.com>
Reviewed-by: Markus Armbruster <armbru@redhat.com>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>

1 files changed, 16 insertions, 0 deletions

diff --git a/hw/pci/msi.c b/hw/pci/msi.c
index a87ef4d752..359058e12c 100644
--- a/hw/pci/msi.c
+++ b/hw/pci/msi.c
@@ -165,6 +165,22 @@ bool msi_enabled(const PCIDevice *dev)
          PCI_MSI_FLAGS_ENABLE);
 }
 
+/*
+ * Make PCI device @dev MSI-capable.
+ * Non-zero @offset puts capability MSI at that offset in PCI config
+ * space.
+ * @nr_vectors is the number of MSI vectors (1, 2, 4, 8, 16 or 32).
+ * If @msi64bit, make the device capable of sending a 64-bit message
+ * address.
+ * If @msi_per_vector_mask, make the device support per-vector masking.
+ * Return the offset of capability MSI in config space on success,
+ * return -errno on error.
+ *
+ * -ENOTSUP means lacking msi support for a msi-capable platform.
+ * -EINVAL means capability overlap, happens when @offset is non-zero,
+ *  also means a programming error, except device assignment, which can check
+ *  if a real HW is broken.
+ */
 int msi_init(struct PCIDevice *dev, uint8_t offset,
              unsigned int nr_vectors, bool msi64bit, bool msi_per_vector_mask)
 {