Re: Accessing file from drivers (fwd)

Hi Wolfgang,

     The exact problem that we're trying to solve, is to program an FPGA with a hex file
which is in our file system.  But the problem is general is to have a way to write  a
system  call  say 'sys_copy'  which will copy one file to another.  An user-mode
application would read from one file and write back to another, which would result in
copying  the data from the file driver ( kernel space ) to the user-space,  and again
back to the kernel space.  We were curious as to whether a way existed by which we can
do the read and write, sitting in the kernel space itself.  Of course adding our own
ioctl to the drivers will serve the purpose,  but we were looking for some way in which
we would NOT need to modify the existing file system drivers.  I was wondering if it
would be possible to bypass the read/write call themselves, but hack our way into the
buffer caches of block drivers, to do this ?   Anyone tried something similar ?

Regards,
Soumya.

---------- Forwarded message ----------
Date: Thu, 15 Mar 2001 15:04:31 +0100
From: Wolfgang Denk <redacted>
To: gopi@tejasnetworks.com
Cc: linuxppc-dev@lists.linuxppc.org
Subject: Re: Accessing file from drivers

In message [off-list ref] you wrote:

quoted

  Is it possible to read and write to files (say /etc/xyz)
in a device driver without resorting to user space?  I want

You do not want to do this. It's bad design. Implement an ioctl() for
the configuration, and use that.

Wolfgang Denk

--
Software Engineering:  Embedded and Realtime Systems,  Embedded Linux
Phone: (+49)-8142-4596-87  Fax: (+49)-8142-4596-88  Email: wd@denx.de
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Hi Wolfgang,

     The exact problem that we're trying to solve, is to program
an FPGA with a hex file
which is in our file system.  But the problem is general is to
have a way to write  a
system  call  say 'sys_copy'  which will copy one file to
another.  An user-mode
application would read from one file and write back to another,
which would result in
copying  the data from the file driver ( kernel space ) to the
user-space,  and again
back to the kernel space.  We were curious as to whether a way
existed by which we can
do the read and write, sitting in the kernel space itself.

I don't know if I well understand the problem, but it seems to me that you
can use the mmap system call ...


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