Hello Rahul, First of all please don't do top-posting rather do bottom-posting. For more information search google. On 10/19/06, Rahul Theraja <rahul.theraja@xxxxxxxxx> wrote:
Hello Shakthi Kannan, Thanks for the reply . > > driver. I could not understand why the "sbd_request " is called even though > > i have given only one read call from user space file. > > Block device I/O transfer is done in blocks. > > > And also in the driver, in the function sbd_request() how does the driver > > get the parameters like sector, current_nr_sectors and buffer. > > VFS <-> SCSI <-> Block device? >
I think its VFS<->Buffer-Cache<->Block-Device and if drive is mounted then VFS<->FS<->Buffer-Cache<->Block-Device
> > i could move > > furhter fastly. > > Fastly? IMHO, learning kernel development involves lot of patience. > > SK Is it necessary to use kernel_thread() in block drivers. In drivers/block loop.c i could see kernel_thread() being used but in floopy.c it is not used. When is this kernel_thread() function is supposed to be used ? In the sbd_device also the kernel_thread() is not used.
First in kernel-2.6.x its better to use kthread_*() rather than kernel_thread if threading is needed. Threading isn't necessary in any device until unless you need it. For example if your driver is emulating a device or performing IO directly then you don't need it, but if your driver is sending request to a device which generates interrupts after completing IO and you want to do some extra work after getting IO completion interrupt then you must use thread. As threads work in process-context, hence can do sleep and lengthy processing but interrupt-context shouldn't sleep or nor do long processing. For getting more understanding about different contexts like process, interrupt, softirqs contexts do search google.
Anyone please kindly clarify my doubts.
I hope you doubts are not clear.
Thanks in Advance -Rahul
-- Fawad Lateef -- Kernelnewbies: Help each other learn about the Linux kernel. Archive: http://mail.nl.linux.org/kernelnewbies/ FAQ: http://kernelnewbies.org/faq/
