I am new to tasklets in Linux. Here I am scheduling 3 tasklets in ISR. But what I observed is that only one tasklet in executed. fill_buf is tasklet_struct and Linux version is 5.10.63. Answer You are scheduling the same tasklet three times in a row, but a tasklet can only be scheduled again if it has already run (or
Tag: linux-device-driver
Can I use ioread32_rep(addr, buf, 2) to replace ioread64()?
I am currently going through Linux Device Drivers book and found the functions for reading from I/O memory: To read from I/O memory, use one of the following: unsigned int ioread8(void *addr); unsigned int ioread16(void *addr); unsigned int ioread32(void *addr); If you must read or write a series of values to a given I/O memory address, you can use the
Get user’s group from linux kernel driver
I’m developing a simple pipe kernel driver as an excercise for university, and my task states that users from each user group should have access to their own separate pipe. But I can’t find how to get group of the user who opened my driver file. I have functon static int pipe_open(struct inode *i, struct file *f) which receives arguments
Should I release data after the use of get_user_pages_fast?
I’m using the get_user_pages_fast, which I allocate a memory buffer in the user and create a pages in the kernel space. Should I free the struct pages** after the use this memory? or call to specific release function? Thanks! Answer From documentation on get_user_pages() (which has similar functionality, but with more parameters, and needs a semaphore held): Each page returned
Ethtool Structs elements and what are they. What settings and info defined on them
I am reading driver code from Intel E1000E AND Realtek r1869 driver. I hvae the devices for both, Currently I am studying ethtool_ops. I know Ethtool can be a tool for Long story short, ethtool is a means to display and adjust generic NIC/driver parameters (identification, the number of receive and transmit queues, receive and transmit offloads, you > name
How are memory regions on ARM Cortex A denoted as “device” or “strongly ordered” under Linux
On the ARM Cortex-A9 that comprises part of the Zynq SoC I’m using, regions of memory are labelled as “normal”, “device” or “strongly ordered”. This is described in the Zynq technical reference manual, but I understand it is a property of ARMs more generally. Obviously, the ability to have strongly ordered memory accesses for memory mapped devices (which includes many
Get Character String Written to Custom /dev/ file
I’m currently working with a custom device driver that I installed. I’m very new to this and having trouble understanding how to get the data that I write into it from the command line. For example, I write data to the file like so: And then I merely want to get the string here, so I can use the characters
Is there a way to lookup refcount for a kobject?
I expected to find a function along the lines of kobject_check_refcount, that returned the current refcount without altering it, in kobject.c, but as far as I can see there isn’t one. Is there such a function existing in the kernel source somewhere? I can see it being useful for debugging purposes at points. Edit: found kref_read which sounds like it
Why do my calls to gpiod_set_value return an “invalid GPIO” error?
I am attempting to write a driver for an OV2680 camera sensor. I want to turn on some GPIO pins as one of the steps in its ->probe() function. Those GpioIo() pins are declared in the DSDT tables like so (for a device upon which the OV2680 is dependent; see full DSDT table: Note absence of a _DSD segment, meaning
Interrupt Handler Stops Working After Kernel Module Reload (Xilinx FPGA / PCIe)
I am currently working on a PCI driver for the Xilinx Kintex 7 board using the Xilinx PCI IP core (AXI Memory Mapped to PCIe). One problem is, that the interrupt handler stops working when I reload the kernel module. In more detail: Fresh boot of my machine Load the kernel module and monitor the kernel messages with dmesg /proc/interrupts