software/kernel/main: Add a few comments.

litepcie/software/kernel/main.c

@@ -137,17 +137,27 @@ static void litepcie_enable_interrupt(struct litepcie_device *s, int irq_num)
 {
 	uint32_t v;
 
+	/* Read the current interrupt enable register value */
 	v = litepcie_readl(s, CSR_PCIE_MSI_ENABLE_ADDR);
+
+	/* Set the bit corresponding to the given interrupt number */
 	v |= (1 << irq_num);
+
+	/* Write the updated value back to the register */
 	litepcie_writel(s, CSR_PCIE_MSI_ENABLE_ADDR, v);
 }
 
 static void litepcie_disable_interrupt(struct litepcie_device *s, int irq_num)
 {
 	uint32_t v;
 
+	/* Read the current interrupt enable register value */
 	v = litepcie_readl(s, CSR_PCIE_MSI_ENABLE_ADDR);
+
+	/* Clear the bit corresponding to the given interrupt number */
 	v &= ~(1 << irq_num);
+
+	/* Write the updated value back to the register */
 	litepcie_writel(s, CSR_PCIE_MSI_ENABLE_ADDR, v);
 }
 
@@ -1000,6 +1010,7 @@ static int litepcie_pci_probe(struct pci_dev *dev, const struct pci_device_id *i
 
 	dev_info(&dev->dev, "\e[1m[Probing device]\e[0m\n");
 
+	/* Allocate memory for the LitePCIe device structure */
 	litepcie_dev = devm_kzalloc(&dev->dev, sizeof(struct litepcie_device), GFP_KERNEL);
 	if (!litepcie_dev) {
 		ret = -ENOMEM;
@@ -1010,6 +1021,7 @@ static int litepcie_pci_probe(struct pci_dev *dev, const struct pci_device_id *i
 	litepcie_dev->dev = dev;
 	spin_lock_init(&litepcie_dev->lock);
 
+	/* Enable the PCI device */
 	ret = pcim_enable_device(dev);
 	if (ret != 0) {
 		dev_err(&dev->dev, "Cannot enable device\n");
@@ -1018,19 +1030,20 @@ static int litepcie_pci_probe(struct pci_dev *dev, const struct pci_device_id *i
 
 	ret = -EIO;
 
-	/* Check device version */
+	/* Check the device version */
 	pci_read_config_byte(dev, PCI_REVISION_ID, &rev_id);
 	if (rev_id != 0) {
 		dev_err(&dev->dev, "Unsupported device version %d\n", rev_id);
 		goto fail1;
 	}
 
-	/* Check bar0 config */
+	/* Check the BAR0 configuration */
 	if (!(pci_resource_flags(dev, 0) & IORESOURCE_MEM)) {
 		dev_err(&dev->dev, "Invalid BAR0 configuration\n");
 		goto fail1;
 	}
 
+	/* Request and map BAR0 */
 	if (pcim_iomap_regions(dev, BIT(0), LITEPCIE_NAME) < 0) {
 		dev_err(&dev->dev, "Could not request regions\n");
 		goto fail1;
@@ -1048,9 +1061,9 @@ static int litepcie_pci_probe(struct pci_dev *dev, const struct pci_device_id *i
 	msleep(10);
 #endif
 
-	/* Show identifier */
+	/* Read and display the FPGA identifier */
 	for (i = 0; i < 256; i++)
-		fpga_identifier[i] = litepcie_readl(litepcie_dev, CSR_IDENTIFIER_MEM_BASE + i*4);
+		fpga_identifier[i] = litepcie_readl(litepcie_dev, CSR_IDENTIFIER_MEM_BASE + i * 4);
 	dev_info(&dev->dev, "Version %s\n", fpga_identifier);
 
 	pci_set_master(dev);
@@ -1062,7 +1075,7 @@ static int litepcie_pci_probe(struct pci_dev *dev, const struct pci_device_id *i
 	if (ret) {
 		dev_err(&dev->dev, "Failed to set DMA mask\n");
 		goto fail1;
-	};
+	}
 
 
 /* MSI-X */
@@ -1089,6 +1102,7 @@ static int litepcie_pci_probe(struct pci_dev *dev, const struct pci_device_id *i
 	for (i = 0; i < irqs; i++) {
 		int irq = pci_irq_vector(dev, i);
 
+		/* Request IRQ */
 		ret = request_irq(irq, litepcie_interrupt, 0, LITEPCIE_NAME, litepcie_dev);
 		if (ret < 0) {
 			dev_err(&dev->dev, " Failed to allocate IRQ %d\n", dev->irq);
@@ -1290,14 +1304,15 @@ static const struct pci_device_id litepcie_pci_ids[] = {
 };
 MODULE_DEVICE_TABLE(pci, litepcie_pci_ids);
 
+/* PCI driver structure */
 static struct pci_driver litepcie_pci_driver = {
 	.name = LITEPCIE_NAME,
 	.id_table = litepcie_pci_ids,
 	.probe = litepcie_pci_probe,
 	.remove = litepcie_pci_remove,
 };
 
-
+/* Module initialization function */
 static int __init litepcie_module_init(void)
 {
 	int ret;
@@ -1337,14 +1352,14 @@ static int __init litepcie_module_init(void)
 	return ret;
 }
 
+/* Module exit function */
 static void __exit litepcie_module_exit(void)
 {
 	pci_unregister_driver(&litepcie_pci_driver);
 	unregister_chrdev_region(litepcie_dev_t, LITEPCIE_MINOR_COUNT);
 	class_destroy(litepcie_class);
 }
 
-
 module_init(litepcie_module_init);
 module_exit(litepcie_module_exit);