linux-device-driver

问题 I am trying to understand the 8250 serial port on pci express bus of our board by going through the driver code and I am having hard time understanding the below two members of struct uart_8250_port struct uart_8250_port x; memset(&x, 0, sizeof(x)); .... .... x.port.regshift = 0; x.port.iotype = UPIO_MEM; x.port.flags = UPF_SHARE_IRQ | UPF_LOW_LATENCY; x.port.membase = raw_address; x.port.mapbase = ioremap(raw_address); What are the members membase and mapbase ? Also, why does membase take

问题 I've got two kernel modules built, one of which is a net_device. My net_device module A depends on module B which provide some extra control mechanism to export device info. Now, I want to be able to call the xmit function in module A from module B. As a result, module B will become dependent on module A if I simple export symbol from A. This, obviously, creates a 'deadlock' like dependency situation. Does anyone have experience resolving this? How can I properly export the xmit function in A

问题 I am trying to learn to write a i2c driver on raspberry pi board and i have taken groove LCD back-light.Here driver.probe is not getting called whereas driver's inserted in system as i can see in dmesg. Init code of driver is getting called, and code => static int lcd_probe(struct i2c_client *i2c_client, const struct i2c_device_id *i2c_id) { int ret = 0; //struct lcd_data *lcd_data; // struct device *dev = &i2c_client->dev; // lcd_data->client = i2c_client; pr_debug("lcd_probe : calling the

问题 I am using 3.10.x kernel tree. My kernel module needs config VIDEOBUF2. That is defined in drivers/media/v4l2-core/Kconfig: # Used by drivers that need Videobuf2 modules config VIDEOBUF2_CORE select DMA_SHARED_BUFFER tristate So I put 'CONFIG_VIDEOBUF2_CORE=y' in my Kernel config file and compile. From the Kconfig it has CONFIG_VIDEOBUF2_CORE has no dependency and I think adding CONFIG_VIDEOBUF2_CORE=y to my kernel config should work. I am modify the right kernel config file since I set other

问题 How to configure the serial port in kernel module. I am doing this in init module function. same configuration is working in userpsace. I am using the below code to configure the serial port. mm_segment_t oldfs; oldfs = get_fs(); set_fs(KERNEL_DS); fp = filp_open("/dev/ttyS0",O_RDWR | O_NOCTTY | O_NDELAY); tty = (struct tty_struct *)fp->private_data; setting the required configuration(tty->termios) set_fs(oldfs); 回答1: Almost all functions of serial port operations are implemented by drivers

问题 here is the simple module program code. #include <linux/module.h> /* Needed by all modules */ #include <linux/kernel.h> /* Needed for KERN_INFO */ #include <linux/init.h> /* Needed for the macros */ static int hello3_data __initdata = 3; static int __init hello_3_init(void) { printk(KERN_INFO "Hello, world %d\n", hello3_data); return 0; } static void __exit hello_3_exit(void) { printk(KERN_INFO "Goodbye, world %d\n",hello3_data); } module_init(hello_3_init); module_exit(hello_3_exit); I've

问题 In an MFD device. I wanted to understand, how do we arrive at irq base . Is it a random number.? Please some one explain. 回答1: Basically one first needs to associate a particular IRQ number with an actual physical hardware interrupt before attempting to register an ISR for that IRQ number. This is commonly done in the Linux kernel using irq_domain_add_linear(). In the past, IRQ numbers could be chosen so they matched the hardware IRQ line into the root interrupt controller (i.e. the component

问题 Context In the device tree I am using, in one of its node, the filed interrupts is: interrupts = <0x0 0x1d 0x4>; (from a device tree of a Pynq board, equipaged with a ZYnq device with a dual-core ARM A9 ) Now, in the device tree .probe function, I use the Linux kernel API: irq_line = platform_get_irq(pdev, 0); in order to get the irq to use for the function request_irq (described in ldd3 chapter 10). Ones the irq_line = platform_get_irq(pdev, 0); is executed, I get the value 0x2e that DOESN'T

问题 I am developing Linux kernel module that communicate with user space program. This module waits for a message which is being sent from user space in order to print it in kernel mode. This is the module : #include <linux/init.h> #include <linux/module.h> #include <linux/fs.h> #include <linux/device.h> #include <linux/kernel.h> #include <linux/uaccess.h> MODULE_LICENSE("GPL"); MODULE_AUTHOR("Gaston"); MODULE_DESCRIPTION("A simple Linux char driver"); MODULE_VERSION("0.1"); #define MAX 256

问题 I want to free a structure with spin_lock is embedded. scenario is as follows: I have two functions f1 () { ***************** spin_lock_irqsave(&my_obj_ptr->my_lock, flags) .... .... ........................................ here f2 is called spin_lock_irqstore(&my_obj_ptr->my_lock, flags) ******************* kfree(my_obj_ptr) } and f2 has similar content with f1. when f2 is called my_lock is being used, f2 must busy waiting. however, when f2 is entering the critical section, my_obj_ptr is