#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
int main(){
FILE *fp;
while(1){
printf("open /proc/myled 1\n");
fp = fopen("/proc/myled", "w");
if (fp=NULL){
printf("cannot open /proc/myled for write\b");
return -1;
}
printf("fputs 0x0F\n");
fputs("0x0F\n", fp); //SEGMENTATION FAULT HAPPENS HERE
printf("fclose 1\n");
fclose(fp);
sleep(1);
In the myled driver I put some printk to see which functions get called. When using the blink.c, the proc_myled_write never even runs.
When I interact with the driver without the C code using echo "0x05\n" >> /proc/myled in the terminal, the proc_myled_write runs, there is no segmentation fault and the LEDs change state.
#include <linux/kernel.h>
#include <linux/module.h>
#include <asm/uaccess.h> /* Needed for copy_from_user */
#include <asm/io.h> /* Needed for IO Read/Write Functions */
#include <linux/proc_fs.h> /* Needed for Proc File System Functions */
#include <linux/seq_file.h> /* Needed for Sequence File Operations */
#include <linux/platform_device.h> /* Needed for Platform Driver Functions */
#include<linux/slab.h>
/* Define Driver Name */
#define DRIVER_NAME "myled"
unsigned long *base_addr; /* Vitual Base Address */
struct resource *res; /* Device Resource Structure */
unsigned long remap_size; /* Device Memory Size */
/* Write operation for /proc/myled
* -----------------------------------
* When user cat a string to /proc/myled file, the string will be stored in
* const char __user *buf. This function will copy the string from user
* space into kernel space, and change it to an unsigned long value.
* It will then write the value to the register of myled controller,
* and turn on the corresponding LEDs eventually.
*/
static ssize_t proc_myled_write(struct file *file, const char __user * buf,
size_t count, loff_t * ppos)
{
char myled_phrase[16];
u32 myled_value;
printk(KERN_INFO "proc_myled_write:");
if (count < 11) {
if (copy_from_user(myled_phrase, buf, count))
return -EFAULT;
myled_phrase[count] = '\0';
}
myled_value = simple_strtoul(myled_phrase, NULL, 0);
printk(KERN_INFO "%i\n", myled_value);
wmb();
iowrite32(myled_value, base_addr);
return count;
}
/* Callback function when opening file /proc/myled
* ------------------------------------------------------
* Read the register value of myled controller, print the value to
* the sequence file struct seq_file *p. In file open operation for /proc/myled
* this callback function will be called first to fill up the seq_file,
* and seq_read function will print whatever in seq_file to the terminal.
*/
static int proc_myled_show(struct seq_file *p, void *v)
{
printk(KERN_INFO "proc_myled_show\n");
u32 myled_value;
printk(KERN_INFO "proc_myled_show ioread32\n");
myled_value = ioread32(base_addr);
printk(KERN_INFO "proc_myled_show seq_printf\n");
seq_printf(p, "0x%x", myled_value);
return 0;
}
/* Open function for /proc/myled
* ------------------------------------
* When user want to read /proc/myled (i.e. cat /proc/myled), the open function
* will be called first. In the open function, a seq_file will be prepared and the
* status of myled will be filled into the seq_file by proc_myled_show function.
*/
static int proc_myled_open(struct inode *inode, struct file *file)
{
unsigned int size = 16;
char *buf;
struct seq_file *m;
int res;
printk(KERN_INFO "proc_myled_open\n");
buf = (char *)kmalloc(size * sizeof(char), GFP_KERNEL);
if (!buf)
return -ENOMEM;
printk(KERN_INFO "proc_myled_open single_open\n");
res = single_open(file, proc_myled_show, NULL);
if (!res) {
m = file->private_data;
m->buf = buf;
m->size = size;
} else {
kfree(buf);
}
printk(KERN_INFO "proc_myled_open end\n");
return res;
}
/* File Operations for /proc/myled */
static const struct file_operations proc_myled_operations = {
.open = proc_myled_open,
.read = seq_read,
.write = proc_myled_write,
.llseek = seq_lseek,
.release = single_release
};
/* Shutdown function for myled
* -----------------------------------
* Before myled shutdown, turn-off all the leds
*/
static void myled_shutdown(struct platform_device *pdev)
{
printk(KERN_INFO "myled_shutdown");
iowrite32(0, base_addr);
}
/* Remove function for myled
* ----------------------------------
* When myled module is removed, turn off all the leds first,
* release virtual address and the memory region requested.
*/
static int myled_remove(struct platform_device *pdev)
{
printk(KERN_INFO "myled_remove");
myled_shutdown(pdev);
/* Remove /proc/myled entry */
remove_proc_entry(DRIVER_NAME, NULL);
/* Release mapped virtual address */
iounmap(base_addr);
/* Release the region */
release_mem_region(res->start, remap_size);
return 0;
}
/* Device Probe function for myled
* ------------------------------------
* Get the resource structure from the information in device tree.
* request the memory regioon needed for the controller, and map it into
* kernel virtual memory space. Create an entry under /proc file system
* and register file operations for that entry.
*/
static int myled_probe(struct platform_device *pdev)
{
printk(KERN_INFO "myled_probe\n");
struct proc_dir_entry *myled_proc_entry;
int ret = 0;
res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
if (!res) {
dev_err(&pdev->dev, "No memory resource\n");
return -ENODEV;
}
printk(KERN_INFO "myled_probe res->star 0x%08lxt\n", res->start );
remap_size = res->end - res->start + 1;
if (!request_mem_region(res->start, remap_size, pdev->name)) {
dev_err(&pdev->dev, "Cannot request IO\n");
return -ENXIO;
}
base_addr = ioremap(res->start, remap_size);
if (base_addr == NULL) {
dev_err(&pdev->dev, "Couldn't ioremap memory at 0x%08lx\n",
(unsigned long)res->start);
ret = -ENOMEM;
goto err_release_region;
}
myled_proc_entry = proc_create(DRIVER_NAME, 0, NULL,
&proc_myled_operations);
if (myled_proc_entry == NULL) {
dev_err(&pdev->dev, "Couldn't create proc entry\n");
ret = -ENOMEM;
goto err_create_proc_entry;
}
printk(KERN_INFO DRIVER_NAME " probed at VA 0x%08lx\n",
(unsigned long) base_addr);
return 0;
err_create_proc_entry:
iounmap(base_addr);
err_release_region:
release_mem_region(res->start, remap_size);
return ret;
}
/* device match table to match with device node in device tree */
static const struct of_device_id myled_of_match[] = {
{.compatible = "dglnt_myled-1.00.a"},
{},
};
MODULE_DEVICE_TABLE(of, myled_of_match);
/* platform driver structure for myled driver */
static struct platform_driver myled_driver = {
.driver = {
.name = DRIVER_NAME,
.owner = THIS_MODULE,
.of_match_table = myled_of_match},
.probe = myled_probe,
.remove = myled_remove,
.shutdown = myled_shutdown
};
/* Register myled platform driver */
module_platform_driver(myled_driver);
/* Module Informations */
MODULE_AUTHOR("Digilent, Inc.");
MODULE_LICENSE("GPL");
MODULE_DESCRIPTION(DRIVER_NAME ": MYLED driver (Simple Version)");
MODULE_ALIAS(DRIVER_NAME);
Question
toastedcpu
Hello,
I am still working on Embedded Linux Tutorial Zybo http://www.instructables.com/id/Embedded-Linux-Tutorial-Zybo/, and I get a segmentation fault on the C blink code where puts is writing to the /proc/myled.
In the myled driver I put some printk to see which functions get called. When using the blink.c, the proc_myled_write never even runs.
When I interact with the driver without the C code using echo "0x05\n" >> /proc/myled in the terminal, the proc_myled_write runs, there is no segmentation fault and the LEDs change state.
zynq> echo "0x05\n" >> /proc/myled
proc_myled_open
proc_myled_open single_open
proc_myled_open end
proc_myled_write:
5
Here is the myled.c file:
Any ideas?
Thanks,
Frank
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