Two main kinds of timing measurement that must be performed by the Linux kernel: Keeping the current time and date, so that they can be returned to user programs through the time( ), ftime( ), and gettimeofday( ) system calls. … Continue reading
The Memory management unit consists of Segmentation unit and Paging unit. Segmentation unit allows the use of two address components, viz. segment and offset for relocability and sharing of code and data. •Segmentation unit allows segments of size 4Gbytes at … Continue reading
In init() it call cdrom_sysctl_register() which initialied different parameter like autoclose, autoeject, debug, lockdoor, check_media_change.
The sequence of instructions executed in Kernel Mode to handle a kernel request is denoted as kernel control path : when a User Mode process issues a system call request, for instance, the first instructions of the corresponding kernel control … Continue reading
??All Unix kernels are reentrant : this means that several processes may be executing in Kernel Mode at the same time. Of course, on uniprocessor systems only one process can progress, but many of them can be blocked in Kernel … Continue reading
In spi communication , master controls the clock for transmission. whenever master has data to be sent , it load the data in SDO and then high the clock status. slave check for high clock and then reads data from … Continue reading
Block drivers often attempt to retry requests that fail the first time. This behavior can lead to a more reliable system and help to avoid data loss. The kernel, however, sometimes marks requests as not being retryable. Such requests should … Continue reading
The Serial Peripheral Interface Bus is a synchronous serial data link standard that operates in full duplex mode. Devices communicate in master/slave mode where the master device initiates the data frame. Multiple slave devices are allowed with individual slave select … Continue reading
prototype of end request function is void end_request(struct request *, int ) here if we pass 0 as second argument if request is not complete and 1 if it’s complete
The bio structure contains everything that a block driver needs to carry out the request without reference to the user-space process that caused that request to be initiated. The bio structure, which is defined in <linux/bio.h>, contains a number of … Continue reading
There are different types of USB devices as they can be used for different purposes. First a device can be self powered, bus powered or both. The USB can provide a power supply up to 500mA for its devices. If … Continue reading
Can anybdy tell me …what are the various steps involved in building of a tool chain in some details…if u hv any kind of docs(what to do after installing Uboot and initrd)..plz tell me…ur comments may fulfil sum1 needs…
Once sbull_open has its device structure pointer, it calls del_timer_sync to remove the “media removal” timer, if any is active. Note that we do not lock the device spinlock until after the timer has been deleted; doing otherwise invites deadlock … Continue reading
Queue creation and deletion request_queue_t *blk_init_queue(request_fn_proc *request, spinlock_t *lock); The arguments are, of course, the request function for this queue and a spinlock that controls access to the queue. This function allocates memory (quite a bit of memory, actually) … Continue reading