Re: [Linux-fbdev-devel] Re: [PATCH] fbdev: colormap fixes

From: Jon Smirl
Date: Thu Jul 28 2005 - 15:55:17 EST

I've verified now that all ATI R300+ chips have 10bit cmaps. These are
pretty common so I'd be in favor of making this into a binary
attribute where I can get/set the whole table at once. Given that
OpenGL is already supporting 12 and 16 bits these tables are only
going to get much larger.

1024 entries * 5 fields * 2 bytes = 10KB -- too big for a text attribute.

65536 entries * 5 fields * 2 bytes = 655KB -- way too big for a text attribute.

The bits_per_pixel sysfs attribute is an easy way to tell how many
entries you need. You can just set it at 4, 8, 10, etc until you get
an error. Now you know the max. 2^n and you know how many entries.

Jon Smirl
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