linux-device-driver

问题 I am trying short.c in examples of Linux Device Driver 3 My PC has Parallel Port and after the Ubuntu boots up, I can see these: cat /proc/ioports 0378-037a : parport0 037b-037f : parport0 outp 0x378 1 (outp is another example in LDD3 which write data to ports) the LED on the port is ON. Then I run these commands to remove modules rmmod lp rmmod parport_pc cat /proc/ioports (There is no module on 0378-037f any more.) I run this again but the LED is not ON this time. outp 0x378 1 Then I

问题 I have a smart card IC module, and I want to create a Linux device driver for it. This module is using SPI as the controlling line and has an interrupt line to indicate whether a card is ready. I know how to create a SPI device in Linux kernel and how to read data in the kernel when the interruption happens. But I have no idea on how to transfer the data to the user space (maybe need to create a device node for it), and how to give the user space a interruption to notify it. Does anyone have

问题 I'm writing a kernel module which involves the tasklist_lock , __bss_start . These symbols are not exported. I'm pretty sure even if not exported, we can access the symbols from text sections using kernsym_lookup_name() Reference How my custom module on linux 3.2.28 can make a call to print_cpu_info? $ vim System.map ... 80017be0 T register_undef_hook 80017c28 T unregister_undef_hook 80017c70 T do_unexp_fiq ... 806eb000 D mmlist_lock 806eb040 D tasklist_lock 806eb080 d softirq_vec .... T

问题 I am trying to interface freescale imx6 SoC with mpu92/65 sensor device. I have taken mpu92/65 device driver from android (https://github.com/NoelMacwan/Kernel-10.4.1.B.0.101/tree/master/drivers/staging/iio/imu ) and have done necessary modifications to the driver and device tree. Device tree modifications: &i2c3{ ... extaccelerometer: mpu9250@68{ compatible = "mpu9250"; reg = <0x68>; interrupt-parent = <&gpio2>; interrupts = <9>; int_config = /bits/ 8 <0x00>; level_shifter = /bits/ 8 <0>;

问题 I can read the status of my laptop lid by reading /proc/acpi/button/lid/LID0/state file. Now I want to read it from kernel module. I found the source file drivers/acpi/button.c in kernel source. But still I didn't understand how to use it. It exporting acpi_lid_notifier_register, acpi_lid_notifier_unregiste and acpi_lid_open functions. How to write a module for lid state? 回答1: acpi_lid_open returns 0 (closed), 1 (open), or a negative error number (unsupported). To use the notifier, you would

问题 Many guides on device driver programming suggest that streaming DMA mappings (i.e. those created by dma_map_single() and friends), be held open for as short a time as possible, as they consume resources (i.e. IOMMU mapping resources if the platform has one, or a bounce buffer when required). In my case, I'm working with a PCIe device capable of 64-bit DMA, so a bounce buffer should be unnecessary (and it doesn't seem like special treatment from the IOMMU is required in this case either,

问题 I am working on a testing tool for nvme-cli(written in c and can run on linux). For SSD validation purpose, we are actually looking for sending I/O commands to a particular Submission queue(IO Queue pair). We needed this because we wanted threading, but for threading to happen we need to send I/O requests to different queues else the I/O requests would be processed serially. So is there any way in ioctl() where we can specify the Submission queue IDs? Here is how a nvme IO is requested with

问题 The host part will be a PC program made from c# in which I will use LibUSBdotnet to do the communication. My problem is how do I make the Linux side pickup and respond. I don't really know where to start. Whenever I try to search for it, all result show are "how linux communicates with a device attached to it". Or it does not matter if a device is host or client, because they utilize the same pipes/bus? Can I use something in "/dev/usb***"? I have seen "libusb" which I believe is the linux

问题 I want to distribute proprietary Linux module for various distros without pre-building the module for all of them. For example I have the following files: wrapp.c mod.c fops.c All wrapp.c is wrapper for all kernel functions I'm using: unsigned int wrap_ioread8(void *addr) { return ioread8(addr); } What I want to do is to give the customer mod.o and fops.o + the wrapp.c. So I build the mod/fops.o on kernel 3.2 then tried to use them on kernel 2.6.32. The module builds without a problem but

问题 I have a custom board with freescale P1010 processor in which P1010's eTSEC2 ( Enhanced 3-speed Ethernet controller) port is directly connected to Marvell 88E6046 ethernet switch Port 9 in SGMII mode. Linux (3.17) DSA driver is able to probe and detect switch ( Port 9 is 'cpu' whereas port 0 and 1 are designated as 'lan1' and 'lan2'). The problem however is, that there is no PHY for switch to attach to ( 'ifconfig up' fails to attach to ethx). U-boot creates a 'generic PHY' eth0 since it