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>

hw/net/vmxnet3.c

@@ -348,7 +348,7 @@ typedef struct {
 /* Interrupt management */
 
 /*
- *This function returns sign whether interrupt line is in asserted state
+ * This function returns sign whether interrupt line is in asserted state
  * This depends on the type of interrupt used. For INTX interrupt line will
  * be asserted until explicit deassertion, for MSI(X) interrupt line will
  * be deasserted automatically due to notification semantics of the MSI(X)

hw/pci-bridge/ioh3420.c

@@ -106,12 +106,14 @@ static int ioh3420_initfn(PCIDevice *d)
     if (rc < 0) {
         goto err_bridge;
     }
+
     rc = msi_init(d, IOH_EP_MSI_OFFSET, IOH_EP_MSI_NR_VECTOR,
                   IOH_EP_MSI_SUPPORTED_FLAGS & PCI_MSI_FLAGS_64BIT,
                   IOH_EP_MSI_SUPPORTED_FLAGS & PCI_MSI_FLAGS_MASKBIT);
     if (rc < 0) {
         goto err_bridge;
     }
+
     rc = pcie_cap_init(d, IOH_EP_EXP_OFFSET, PCI_EXP_TYPE_ROOT_PORT, p->port);
     if (rc < 0) {
         goto err_msi;
@@ -120,18 +122,21 @@ static int ioh3420_initfn(PCIDevice *d)
     pcie_cap_arifwd_init(d);
     pcie_cap_deverr_init(d);
     pcie_cap_slot_init(d, s->slot);
+    pcie_cap_root_init(d);
+
     pcie_chassis_create(s->chassis);
     rc = pcie_chassis_add_slot(s);
     if (rc < 0) {
         goto err_pcie_cap;
     }
-    pcie_cap_root_init(d);
+
     rc = pcie_aer_init(d, IOH_EP_AER_OFFSET, PCI_ERR_SIZEOF);
     if (rc < 0) {
         goto err;
     }
     pcie_aer_root_init(d);
     ioh3420_aer_vector_update(d);
+
     return 0;
 
 err:

hw/pci-bridge/pci_bridge_dev.c

@@ -68,10 +68,12 @@ static int pci_bridge_dev_initfn(PCIDevice *dev)
         /* MSI is not applicable without SHPC */
         bridge_dev->flags &= ~(1 << PCI_BRIDGE_DEV_F_MSI_REQ);
     }
+
     err = slotid_cap_init(dev, 0, bridge_dev->chassis_nr, 0);
     if (err) {
         goto slotid_error;
     }
+
     if ((bridge_dev->flags & (1 << PCI_BRIDGE_DEV_F_MSI_REQ)) &&
         msi_nonbroken) {
         err = msi_init(dev, 0, 1, true, true);
@@ -79,6 +81,7 @@ static int pci_bridge_dev_initfn(PCIDevice *dev)
             goto msi_error;
         }
     }
+
     if (shpc_present(dev)) {
         /* TODO: spec recommends using 64 bit prefetcheable BAR.
          * Check whether that works well. */
@@ -86,6 +89,7 @@ static int pci_bridge_dev_initfn(PCIDevice *dev)
                          PCI_BASE_ADDRESS_MEM_TYPE_64, &bridge_dev->bar);
     }
     return 0;
+
 msi_error:
     slotid_cap_cleanup(dev);
 slotid_error:

hw/pci-bridge/xio3130_downstream.c

@@ -70,11 +70,13 @@ static int xio3130_downstream_initfn(PCIDevice *d)
     if (rc < 0) {
         goto err_bridge;
     }
+
     rc = pci_bridge_ssvid_init(d, XIO3130_SSVID_OFFSET,
                                XIO3130_SSVID_SVID, XIO3130_SSVID_SSID);
     if (rc < 0) {
         goto err_bridge;
     }
+
     rc = pcie_cap_init(d, XIO3130_EXP_OFFSET, PCI_EXP_TYPE_DOWNSTREAM,
                        p->port);
     if (rc < 0) {
@@ -83,12 +85,14 @@ static int xio3130_downstream_initfn(PCIDevice *d)
     pcie_cap_flr_init(d);
     pcie_cap_deverr_init(d);
     pcie_cap_slot_init(d, s->slot);
+    pcie_cap_arifwd_init(d);
+
     pcie_chassis_create(s->chassis);
     rc = pcie_chassis_add_slot(s);
     if (rc < 0) {
         goto err_pcie_cap;
     }
-    pcie_cap_arifwd_init(d);
+
     rc = pcie_aer_init(d, XIO3130_AER_OFFSET, PCI_ERR_SIZEOF);
     if (rc < 0) {
         goto err;

hw/pci-bridge/xio3130_upstream.c

@@ -66,11 +66,13 @@ static int xio3130_upstream_initfn(PCIDevice *d)
     if (rc < 0) {
         goto err_bridge;
     }
+
     rc = pci_bridge_ssvid_init(d, XIO3130_SSVID_OFFSET,
                                XIO3130_SSVID_SVID, XIO3130_SSVID_SSID);
     if (rc < 0) {
         goto err_bridge;
     }
+
     rc = pcie_cap_init(d, XIO3130_EXP_OFFSET, PCI_EXP_TYPE_UPSTREAM,
                        p->port);
     if (rc < 0) {
@@ -78,6 +80,7 @@ static int xio3130_upstream_initfn(PCIDevice *d)
     }
     pcie_cap_flr_init(d);
     pcie_cap_deverr_init(d);
+
     rc = pcie_aer_init(d, XIO3130_AER_OFFSET, PCI_ERR_SIZEOF);
     if (rc < 0) {
         goto err;

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)
 {