On 10/20/06, Fawad Lateef <fawadlateef@xxxxxxxxx> wrote:
oh sorry for that
thank you very much for all the help
Hello Rahul,
First of all please don't do top-posting rather do bottom-posting. For
more information search google.
oh sorry for that
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.
thank you very much for all the help
> Thanks in Advance
>
> -Rahul
>
--
Fawad Lateef
