question about drivers/media/dvb-frontends/rtl2830.c

question about drivers/media/dvb-frontends/rtl2830.c

[Julia Lawall]

The function rtl2830_init contains the code:

         buf[0] = tmp << 6;
         buf[0] = (if_ctl >> 16) & 0x3f;
         buf[1] = (if_ctl >>  8) & 0xff;
         buf[2] = (if_ctl >>  0) & 0xff;

Is there any purpose to initializing buf[0] twice?

julia

Re: question about drivers/media/dvb-frontends/rtl2830.c

[Andy Walls]

Julia Lawall <julia.lawall@lip6.fr> wrote:

>The function rtl2830_init contains the code:
>
>         buf[0] = tmp << 6;
>         buf[0] = (if_ctl >> 16) & 0x3f;
>         buf[1] = (if_ctl >>  8) & 0xff;
>         buf[2] = (if_ctl >>  0) & 0xff;
>
>Is there any purpose to initializing buf[0] twice?
>
>julia
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Hmm.  Since 0x3f is the lowest 6 bits, it looks like the second line should use |= instead of = .   I don't know anything about the rt2830 though.

-Andy

Re: question about drivers/media/dvb-frontends/rtl2830.c

[Antti Palosaari]

On 08/26/2012 02:20 PM, Andy Walls wrote:
> Julia Lawall <julia.lawall@lip6.fr> wrote:
>
>> The function rtl2830_init contains the code:
>>
>>          buf[0] = tmp << 6;
>>          buf[0] = (if_ctl >> 16) & 0x3f;
>>          buf[1] = (if_ctl >>  8) & 0xff;
>>          buf[2] = (if_ctl >>  0) & 0xff;
>>
>> Is there any purpose to initializing buf[0] twice?
>>
>> julia
>> --
>> To unsubscribe from this list: send the line "unsubscribe linux-media"
>> in
>> the body of a message to majordomo@vger.kernel.org
>> More majordomo info at  http://vger.kernel.org/majordomo-info.html
>
> Hmm.  Since 0x3f is the lowest 6 bits, it looks like the second line should use |= instead of = .   I don't know anything about the rt2830 though.
>
> -Andy

Andy is correct. If you look few lines just before that you could see 
that logic. Patch is welcome.

regards
Antti


-- 
http://palosaari.fi/

Re: question about drivers/media/dvb-frontends/rtl2830.c

[Julia Lawall]

On Sun, 26 Aug 2012, Antti Palosaari wrote:

> On 08/26/2012 02:20 PM, Andy Walls wrote:
>> Julia Lawall <julia.lawall@lip6.fr> wrote:
>> 
>>> The function rtl2830_init contains the code:
>>>
>>>          buf[0] = tmp << 6;
>>>          buf[0] = (if_ctl >> 16) & 0x3f;
>>>          buf[1] = (if_ctl >>  8) & 0xff;
>>>          buf[2] = (if_ctl >>  0) & 0xff;
>>> 
>>> Is there any purpose to initializing buf[0] twice?
>>> 
>>> julia
>>> --
>>> To unsubscribe from this list: send the line "unsubscribe linux-media"
>>> in
>>> the body of a message to majordomo@vger.kernel.org
>>> More majordomo info at  http://vger.kernel.org/majordomo-info.html
>> 
>> Hmm.  Since 0x3f is the lowest 6 bits, it looks like the second line should 
>> use |= instead of = .   I don't know anything about the rt2830 though.
>> 
>> -Andy
>
> Andy is correct. If you look few lines just before that you could see that 
> logic. Patch is welcome.

Done.  Thanks for the quick responses.

julia