Re: [PATCH] Add support for sq905 based cameras to gspca

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On Tue, 3 Feb 2009, Jean-Francois Moine wrote:

On Tue, 3 Feb 2009 13:15:58 -0600 (CST)
kilgota@xxxxxxxxxxxxxxxxxxxxxx wrote:

Why is there 2 sq905 processes?

I of course do not fully understand why there are two such processes.
However, I would suspect that [sq905/0] is running on processor 0 and
[sq905/1] is running on processor 1. As I remember, there is only one
[sq905] process which runs on a single-core machine.

Indeed, the problem is there! You must have only one process reading the
webcam! I do not see how this can work with these 2 processes...

The problem, then, would seem to me to boil down to the question of whether that is up to us. Apparently, a decision like that is not up to us, but rather it is up to the compiler and to the rest of the kernel to decide. Which, incidentally, appears to me to be a very logical way to arrange things. Presumably, a dual- or multi-core machine gives certain advantages, or it ought to, but it also requires certain accommodations.

You know, Jean-Francois, in a way it is a lucky accident that I got this machine for Christmas. I would never have fired up the Pentium 4, at least until sometime in the unforeseeable future, because in fact I was getting quite adequate performance out of the old Sempron box. Thus, I would not have been aware of this problem, either. We would have gone right ahead, Adam and I, blissfully ignorant, and published a module which has a flaw on a dual-core machine. So, in spite of the problems I say it is better to face the problems now.

Theodore Kilgore
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