[fbdev_backend]: support of DIRECTCOLOR Frame buffer

[Bill Spitzak]

On 06/10/2013 03:18 AM, Pekka Paalanen wrote:
> On Fri, 7 Jun 2013 17:13:59 +0200
> Marc Chalain <marc.chalain at gmail.com> wrote:

>> +    cmap->start = 0;
>> +    cmap->len = cols;
>> +    cmap->red = colors;
>> +    cmap->blue = colors;
>> +    cmap->green = colors;
>
> If there actually is a difference between rcols, gcols, and bcols,
> should you not compute a different a 'colors' array for each different
> _cols?

I don't know if this cmap structure could be changed, but it would be a 
lot easier if it was a single 2-D array, indexed as 
cmap->map[index][channel].

Structures like this usually mean I have to make a kludge so that I can 
turn an index number back into a location, for instance on this I would 
do something like "((&cmap->red)+channel)[index]".

May want to add an alpha channel as well? Though I suspect most systems 
doing direct color only have a single non-opaque color...

> Now, 'colors' is malloc'd here. How does the caller of this function
> know what to free? Freeing each of cmap->{red,blue,green,transp} would
> lead to double-free errors.

 > Right, you free only 'red'. But that's rather surprising.

Changing it to a single 2-d array would fix this mystery as well.