1. Interrupt Handling:
- PCI devices can generate interrupts to signal events to the CPU. We can register interrupt handlers in the kernel to handle these interrupts. Here's an example code snippet that demonstrates registering an interrupt handler for a PCI device:
#include <linux/interrupt.h>
irqreturn_t my_interrupt_handler(int irq, void *dev_id)
{
/* Handle the interrupt */
pr_info("Interrupt occurred on IRQ %d\n", irq);
/* Return IRQ_HANDLED to indicate successful handling */
return IRQ_HANDLED;
}
int register_interrupt_handler(void)
{
int irq = 10; // Example IRQ number
int ret;
/* Register interrupt handler */
ret = request_irq(irq, my_interrupt_handler, IRQF_SHARED, "my_device", NULL);
if (ret) {
pr_err("Failed to register interrupt handler\n");
return ret;
}
return 0;
}
2. Memory Mapping and DMA:
- PCI devices often require access to system memory for data transfer. Memory mapping and Direct Memory Access (DMA) are used for efficient data transfer between devices and memory. Here's an example code snippet that demonstrates memory mapping and DMA setup:
#include <linux/dma-mapping.h>
void map_device_memory(struct pci_dev *pdev)
{
dma_addr_t dma_addr;
void *virt_addr;
/* Map device memory to CPU address space */
virt_addr = pci_iomap(pdev, 0, PAGE_SIZE);
if (!virt_addr) {
pr_err("Failed to map device memory\n");
return;
}
/* Perform DMA transfer */
dma_addr = dma_map_single(pdev->dev, virt_addr, PAGE_SIZE, DMA_FROM_DEVICE);
if (dma_mapping_error(pdev->dev, dma_addr)) {
pr_err("DMA mapping failed\n");
return;
}
}
3. Power Management:
- Power management is essential for controlling the power state of PCI devices to conserve energy and extend device lifespan. Here's an example code snippet that demonstrates power management features:
#include <linux/pm.h>
int my_suspend(struct device *dev)
{
/* Perform device-specific actions during system suspend */
pr_info("Device suspended\n");
return 0;
}
int my_resume(struct device *dev)
{
/* Perform device-specific actions during system resume */
pr_info("Device resumed\n");
return 0;
}
static const struct dev_pm_ops my_pm_ops =
{
.suspend = my_suspend,
.resume = my_resume,
};
void register_power_management(struct pci_dev *pdev)
{
/* Register power management callbacks */
pdev->dev.pm = &my_pm_ops;
}
These code examples provide practical insight into PCI device initialization, interrupt handling, memory mapping, DMA, and power management in Linux.
#linuxdevicedrivers #ldd #linuxlovers
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