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SubjectRe: [PATCH] embarassing typo
Date
Vicente Feito <vicente.feito@gmail.com> writes:

> On Tuesday 29 March 2005 09:58 pm, you wrote:
>> Måns Rullgård wrote:
>> > "Ronald S. Bultje" <rbultje@ronald.bitfreak.net> writes:
>> >>--- linux-2.6.5/drivers/media/video/zr36050.c.old 16 Sep 2004 22:53:27
>> >> -0000 1.2 +++ linux-2.6.5/drivers/media/video/zr36050.c 29 Mar 2005
>> >> 20:30:23 -0000 @@ -419,7 +419,7 @@
>> >> dri_data[2] = 0x00;
>> >> dri_data[3] = 0x04;
>> >> dri_data[4] = ptr->dri >> 8;
>> >>- dri_data[5] = ptr->dri * 0xff;
>> >>+ dri_data[5] = ptr->dri & 0xff;
>> >
>> > Hey, that's a nice obfuscation of a simple negation.
>>
>> It's not a negation. This statement always assigns zero to
>> dri_data[5] if dri_data is char[]. Looks like gcc isn't catching
>> this problem.
>>
> As long as the variable doesn't get overflowed you would have a
> negation, you shouldn't do dri_data[5] = ptr->dri * 0xff; if
> ptr->dri it's 255, but if ptr->dri = 1 i.e. (like is set in
> zr36050_setup) then you would be getting the negation, -1. the
> Direct rendering support is a flag afaik, so in this case I believe
> is a worthy C obfuscated negation code :)
> btw, are you sure about this patch?I would contact the maintainer
> first, because and'ing that doesn't make much sense...

It seems pretty obvious to me, that the code is supposed to store the
high byte in dri_data[4], and the low byte in dri_data[5]. Mistyping
& as * doesn't seem too unlikely, either.

--
Måns Rullgård
mru@inprovide.com

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