Device Drivers Interview Preparation Guide
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Device Drivers frequently Asked Questions by expert members with experience in Linux Device Drivers. These questions and answers will help you strengthen your technical skills, prepare for the new job test and quickly revise the concepts

19 Linux Device Drivers Questions and Answers:

Linux Device Drivers Interview Questions and Answers

1 :: If we use a driver for various device files, then:
a) minor number will be different for every device file
b) minor number will be same for every device file
c) minor number can not be allocated for any device file
d) none of the mentioned

a) minor number will be different for every device file

2 :: In linux kernel 2.1, the minor numbers were used to:
a) represent the sub-functionalitites of the driver
b) identify the driver
c) represent the device files
d) none of the mentioned

a) represnt the sub-functionalitites of the driver

3 :: In linux, a device driver can work without the:
a) major number
b) minor number
c) device file name
d) none of the mentioned

d) none of the mentioned

4 :: In we use a driver for N number of files, then we have to create ____ device files.
a) N
b) 1
c) N-1
d) none of the mentioned

a) N

5 :: The minor number range should be:
a) 0 to 15
b) 0 to 63
c) 0 to 255
d) none of the mentioned

c) 0 to 255

6 :: Which one of the following is not true?
a) dynamic allocation of major numbers is not possible
b) major number can not be shared among drivers
c) both (a) and (b)
d) none of the mentioned

c) both (a) and (b)

7 :: What is the output of this program?

#include<stdio.h>
#include<stdlib.h>
#include<string.h>

int main()
{
int ptr;
ptr = (int)malloc(sizeof(int)*10);
return 0;
}
a) syntax error
b) segmentaion fault
c) run time error
d) none of the mentioned

d) none of the mentioned
Explanation:
The memory has been allocated but we can not access rest of the memory other than 4 bytes.
Output:
[root@localhost google]# gcc -o san san.c
[root@localhost google]# ./san
[root@localhost google]#

8 :: What is the output of this program?

#include<stdio.h>
#inlcude<stdlib.h>

int main()
{
int ptr;
double ptr;
printf("%dn",sizeof(ptr));
return 0;
}
a) 4
b) 8
c) the compiler will give the error
d) segmentaion fault

c) the compiler will give the error
Explanation:
Just see the output carefully.
Output:
[root@localhost google]# gcc -o san san.c
san.c: In function 'main':
san.c:8:10: error: conflicting types for 'ptr'
san.c:7:7: note: previous declaration of 'ptr' was here
[root@localhost google]#

9 :: In this program the two printed memory locations has the difference of ___ bytes.

#include<stdio.h>
#include<stdlib.h>

int main()
{
int ptr;
ptr = (int)malloc(sizeof(int)*2);
printf("%pn",ptr);
printf("%pn",ptr+1);
return 0;
}
a) 1
b) 4
c) can not be determined
d) none of the mentioned

b) 4
Explanation:
Pointer will increment by 4 bytes because it is the types of integer.
Output:
[root@localhost google]# gcc -o san san.c
[root@localhost google]# ./san
0x9b4e008
0x9b4e00c
[root@localhost google]#

10 :: Which one of the following in true about this program?

#include<stdio.h>
#include<stdlib.h>
#include<string.h>

int main()
{
char ptr;
printf("%pn",ptr);
ptr = (char )malloc(sizeof(char));
printf("%pn",ptr);
return 0;
}
a) this program will give segmentation fault
b) this program will print two same values
c) this program has some syntax error
d) none of the mentioned

d) none of the mentioned
Explanation:
This program will print two different values.
Output:
[root@localhost google]# gcc -o san san.c
[root@localhost google]# ./san
0x4a77cff4
0x980c008
[root@localhost google]#

11 :: What is the output of this program?

#include<stdio.h>
#include<stdlib.h>
#include<string.h>

int main()
{
char ptr;
ptr = (char)malloc(sizeof(char)11);
strcpy(ptr,"google");
printf("%dn",ptr);
return 0;
}
a) s
b) google
c) 115
d) segmentation fault

c) 115
Explanation:
This program will print the equivalent decimal value at location pointed by "ptr".
Output:
[root@localhost google]# gcc -o san san.c
[root@localhost google]# ./san
115
[root@localhost google]#

12 :: Tell me what is the output of this program?

#include<stdio.h>
#include<stdlib.h>
#include<string.h>

int main()
{
char *ptr;
memcpy(ptr,"google",11);
printf("%sn",ptr);
return 0;
}
a) google
b) segmentation fault
c) syntax error
d) none of the mentioned

b) segmentation fault
Explanation:
Memory must be allocated to pointer "ptr".
Output:
[root@localhost google]# gcc -o san san.c
[root@localhost google]# ./san
Segmentation fault (core dumped)
[root@localhost google]#