Re: unwanted double reads in /proc routines


Bernhard Holzmayer wrote:
can anyone please help me to shed some light onto this strange behavior.
Here are the facts:
device driver (kernel 2.6.8) using /proc entries to communicate.

Now, I see the printk() message twice (!!) for every read which I issue like
"cat /proc/.../state"
The response is ok.

If I leave out the line *eof=1; there are even three (!) lines from printk.

Who does understand this?

Hi, does the offset value change from one call to the other one? I had
the same problem and even if I was setting *eof to 1, the routine was
called a second time with an offset value set to the amount of data I
returned in the first call.. It seems that the read routine is called
untill it returns 0 (any other better explaination would be appreciated
:) )

I solved the problem by adding

if (offset != 0) {
*eof = 1;
return 0;
}

at the beginning of the function.. This is fine for me, since I write
only few data and it should not be necessary to make multiple read
calls to read it.

Hope it helps..

.

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