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Date: Thu, 27 Mar 1997 21:49:40 -0500
From: Randall Hopper <rhh@ct.picker.com>
To: Amancio Hasty <hasty@rah.star-gate.com>
Cc: multimedia@FreeBSD.ORG
Subject: Re: Bt848 enhancements for this week
References: <199703261237.HAA02315@netwolf.NetMasters.com> <199703261902.LAA05311@rah.star-gate.com>
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Amancio Hasty:
 |For apps which write directly to the vga's linear frame buffer you want
 |to be able to set the correct pixel order for the card. And for apps
 |which don't write directly to the frame buffer you can save  byte
 |swapping in the X server by presenting a matching pixel order to
 |the X server.
 |
 |We need a way to modify IOCTL_GEO_RGB16 and IOCTL_GEO_RGB24 to pass along
 |the pixel order. Then in build_dma_prog set the appropiate
 |bits for bktr_color_ctl based upon capturing even, odd  , or even and odd
 |frame, and the color depth 16 bits vs 32bits.

What might be a nice interface for this is to have the driver accept 4 GEO
values:  the pixel depth, and 32-bit masks for R, G, and B:

          GEO_DEPTH
          GEO_R_MASK
          GEO_G_MASK
          GEO_B_MASK

This is general and would cover byte swapping as well as being able to
support other pixel formats supported by the hardware (e.g. 5-6-5 16bpp).
The driver can fail the "set" ioctl for unsupported formats.  

>From an app perspective, a QUERY_GEO ioctl to get the supported formats
would be a useful API to have along side.

Randall