DEVICE FILE AND INPUT OUTPUT SUBSYSTEMS MANAGEMENT

DEVICE FILE AND INPUT OUTPUT SUBSYSTEMS MANAGEMENT

1. DEVICE FILE AND INPUT OUTPUT SUBSYSTEMS MANAGEMENT 1/25/2015 J.SUDARSHANREDDY

2. Device manager ( inside OR outside kernel space ) is the software that manages these for all. The manager co-ordinates B/W application process , driver and device- controller. The device manager polls the requests at the devices and the actions occur as per their priorities . The device manager manages input & output interrupt queues . 1/25/2015 J.SUDARSHANREDDY

3. The device Manager creates an appropriate kernel interface & API , and that activate the control register - specific actions of the device . The device controller is activated through the API and kernel interface . An ‘OS’ device manager provides & executes the modules for managing the devices & their driver ISR’s . 1/25/2015 J.SUDARSHANREDDY

4. If manages the physical as well as virtual devices like the pipes and sockets through a common strategy . Device management has 3 standard approaches to 3 types of device drives Programmed I/O’s by polling the service need from each device . Interrupt from the device driver ISR and DMA operation used by the devices to access the memory. A device manager has the functions given 1/25/2015 J.SUDARSHANREDDY

5. FUNCTION OF A DEVICE MANAGER: FUNCTION ACTION Device detection & addition Provides the codes for detect- ing the presence of various devices. Then the adding them for the use of os device driver. Device detection Provides the codes for deny- ing the device resonance. Resticate device to specific process Resticate a device access to one process only an instant. Device access manage Sequential access Random access. 1/25/2015 J.SUDARSHANREDDY

6. SET OF COMMAND FUNCTIONS FOR DEVICE: COMMANDS ACTION Create & open Creating & configuring & Initializing the device. Write Write into the device buffer. Read Read from the device buffer. Close & delete Close is for de-registering the device from the system & delete is for close & deleting the device. 1/25/2015 J.SUDARSHANREDDY

7. FILE SYSTEM ORGANISATION & IMPLEMENTATION : 1. A file is named entity on a magnetic disk, optical disk or system memory. 2. A file contains the data, characters & texts. 3. It may also have a mix of each os may have differing abstracts of a file. *A file may be a named entity that is a structured record as on a disk having random access in the system. 1/25/2015 J.SUDARSHANREDDY

8. * A file may be a structured record on a RAM analogous to disk & may also be either separately called RAM disk or simply a file. * A file may be an unstructured record of bits or byte’s. 1/25/2015 J.SUDARSHANREDDY

9. SET OF COMMAND FUNCTIONS IN THE PORTABLE OS (POSIX) FILE S\M : COMMAND IN POSIX ACTIONS Open Creating the file Write Writing the file Read Reading the file Close Closing the file 1/25/2015 J.SUDARSHANREDDY

10. SET OF COMMAND FUNCTIONS IN THE PORTABLE OS (POSIX) FILE S\M : COMMAND IN POSIX ACTIONS Open Creating the file Write Writing the file Read Reading the file Close Closing the file 1/25/2015 J.SUDARSHANREDDY

11. TYPES OF FILE SYSTEM : BLOCK FILE SYSTEM : It’s application generates records to be saved into the memory. These are first structured into a suitable format & then translated into block systems. Byte stream file system : It’s application generates record streams. These streams are to be saved into the memory. 1/25/2015 J.SUDARSHANREDDY

12. I/O SUBSYTEMS: I/O ports are the OS device management subsystems. Drivers communicate with the many devices that use them. I/O instructions depend on the hardware platform. I/O subsystems differ in different OS’s. 1/25/2015 J.SUDARSHANREDDY

13. TYPES OF I/O OPERATIONS: Synchronous: There are may be saperate functions in RTOS. In case of traditional OS it is supperate . These are at certain fixed data transfer rates. A task blocks tills completion of the I/O. e.g. A write function, write () for 1KB data transfer to a buffer. 1/25/2015 J.SUDARSHANREDDY

14. 2) Asynchronous: Asynchronous I/O operations are at the variable data transfer rates. If provisions for a process of high priority not blocked during the I/O’s. 1/25/2015 J.SUDARSHANREDDY

15. I/O SUBSYSTEM IN A TYPICAL OS: SUBSYTEM’S HIERARCHY ACTIONS & LAYERS Application An application having a sub layer between the application & I/O Functions. I/O device driver Functions These are device dependent OS Functions. A driver may interface with a set Of library functions. 1/25/2015 J.SUDARSHANREDDY