Re: help in block drivers

[Rahul <rahul.theraja@gmail.com>]

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On 10/22/06, Rahul <rahul.theraja@gmail.com> wrote:
>
>
>
> On 10/20/06, Fawad Lateef <fawadlateef@gmail.com> wrote:
> >
> > 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@gmail.com > 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.
>
>
Can anyone tell me or send me some links that tells about the following
functions:
daemonize, siginitsetinv , recalc_sigpending . Though i googled, i coildnt
get much information on them.

Thanks in adavance
Rahul



thank you very much for all the help
>
> >  Thanks in Advance
> > >
> > >  -Rahul
> > >
> >
> > --
> > Fawad Lateef
> >
>
>

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