Qualcomm Interview Question Software Engineer / Developers
to be more specific. When an ISR is requested,
1. The return address and CPSR(status) are pushed to stack.
Inside the ISR
1. In case of ARM you need to decrease the Link register by a value of 4. (Adjustment due to Pipeline. ISR always occurs during execution stage of pipeline. at this time CPU will be fetching a instruction ahead of next)
2. Push scratch registers and link register to stack.
3. do the handling
4. and return from ISR using a STDMFD LR {scratch regs,pc}^.
Hi,
Well I was asked the same Qs what u had been asked,had my interview on the 11th of August..for the position of Embedded Software Engineer-Drivers position, what was the position for which you had your interview and when...can u give out some details..
Hello nishit no I was interviewed for another position actually,user
space programming,but he asked all this kernel level.
So did you hear from them again?
It has been 3 weeks almost and I didn't hear from them even after contacting them..
Is it reject.. Any ideas of how qualcomm replies to the interviewees after phone screens
yes, I had cleared the phone interview and was selected for on-site...my on site interview was on the 11th and am waiting for the result....
Following actions are performed in a typical Linux based interrupt service routine.
1. The PIC raises the interrupt line of the CPU
2. CPU suspends the current execution and recognizes that the interrupt needs attention
3. Jumps to IDT (interrupt descriptor table) installed while requesting the IRQ by the device and recognizes the interrupt service routine to run
4. The CPU runs the ISR (may run more than one ISR if the IRQ is shared)
5. The ISR recognizes the interrupt and acknowledges to the PIC
6. Saves IRQ number and the CPU register contents on to the kernel mode stack
7. Schedule bottom half mechanisms if the interrupt needs more deferred processing
May be he expects one of following things:
- S3 October 03, 20091. Interrupt code shouldn't have any lock or other things which may delay/block execution of ISR.
2. Basically ISR could be either a kernel function (in case of system call) OR a function in the device driver code.
3. Minimum amount of work will be done immediately and most of the work will be assigned to the kernel subsystem such as different queues.
4. The ISR must save the context and restore it again.