writing from kernel

can anyone tell me how to write into i file from kernel space. i tried sys_open,sys_write functions bbbbbut they don't work from
my module.

anil

Hi,

As far as I understand the general oppinion on this list :-) the preferred method is to have your module preset a character-device to userspace. Then use a small program to do the I/O.

This normally keeps your kernel module simple and allows for arbitrary compex I/O in userspace.

Chris

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Zen engineering?
-- Jim Griffith

Hi,

Patch below will allow for mounting of root from a DAC960 raid device This has been submitted before (Leonard,Oliver,others), but I'll submit it again.

Reason:
Needed to boot of a DAC960 raid device

Precedents/Justification for Patch:
Root support for compaq raid is included
Root support for ata raid is included
DAC960 driver is included but root support is not

Cheers
Rick

diff -ur linux-2.4.20/init/do_mounts.c linux/init/do_mounts.c
@@ -164,6 +164,24 @@
        { "dasdg", (DASD_MAJOR << MINORBITS) + (6 << 2) },
        { "dasdh", (DASD_MAJOR << MINORBITS) + (7 << 2) },
 #endif
+#if defined(CONFIG_BLK_DEV_DAC960) || defined(CONFIG_BLK_DEV_DAC960_MODULE)
+       { "rd/c0d0p",0x3000 },
+       { "rd/c0d1p",0x3008 },
+       { "rd/c0d2p",0x3010 },
+       { "rd/c0d3p",0x3018 },
+       { "rd/c0d4p",0x3020 },
+       { "rd/c0d5p",0x3028 },
+       { "rd/c0d6p",0x3030 },
+       { "rd/c0d7p",0x3038 },
+       { "rd/c0d8p",0x3040 },
+       { "rd/c0d9p",0x3048 },
+       { "rd/c0d10p",0x3050 },
+       { "rd/c0d11p",0x3058 },
+       { "rd/c0d12p",0x3060 },
+       { "rd/c0d13p",0x3068 },
+       { "rd/c0d14p",0x3070 },
+       { "rd/c0d15p",0x3078 },
+#endif
 #if defined(CONFIG_BLK_CPQ_DA) || defined(CONFIG_BLK_CPQ_DA_MODULE)
        { "ida/c0d0p",0x4800 },
        { "ida/c0d1p",0x4810 },

That is rarely a good idea. But if you insist on doing it anyway, you could use filp_open and the methods in the returned struct. I have an old code example here:

http://www.daimi.au.dk/~kasperd/linux_kernel/kcp.c

Kasper Dupont -- der bruger for meget tid på usenet.
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for(_=52;_;(_%5)||(_/=5),(_%5)&&(_-=2))putchar(_);

As others already pointed out, it's not always a good idea to do this from kernel space. However, if you still want to do it, see snippet below. If you want to write, you have to copy kernel_read() from fs/exec.c and modify it for writing.

Regards, Olaf.

--cut here-->8--
#include <linux/fs.h>

struct file *filp;
unsigned long offset = 0;
char buf[1024];
int n;

filp = filp_open("/path/to/some/file", O_RDONLY, 0); if (!filp || IS_ERR(filp)) {
/* do some error handling */
}

n = kernel_read(filp, offset, buf, sizeof(buf));
if (n != sizeof(buf)) {
/* do some checking */
}

filp_close(filp, 0);
--8<--cut here--