nanogui: linux framebuffer vs. linear video driver ???
Subject:
Re: [nanogui] linux framebuffer vs. linear video driver ???
From:
"Greg Haerr" ####@####.####
Date:
12 Sep 2004 23:54:31 +0100
Message-Id: <0c1d01c4991b$25a98590$3eba46a6@winXP>
: I wonder if it would be faster to use a dedicated linear video driver
: instead of the linux framebuffer device (/dev/fb0).
Generally, it's a lot faster to use the linux fb device, since
you only have to write memory for the graphics to appear,
versus having to twiddle I/O space, etc. For instance,
the standard VGA driver (non-memory mapped) is considerably
more complex.
:
: Are there other reasons not to use the linux framebuffer?
Only if your OS doesn't support it, then one of the more general
libraries is generally used.
:
: I noticed the file drivers/fblin4sa1100.c. Is it use in addition to
/dev/fb0
: or instead of?
The drivers/fblin{1,2,4,8,16,24,32} drivers are all included in
the standard Microwindows build. When Microwindows first
starts up, it queries the kernel for the bits per pixel (BPP) that
the framebuffer requires, and then loads in function pointers
that use one of the above specific linear fb drivers. The
fblin4sa100.c is a replacement driver for the standard fblin4.c
driver. IIRC, it is a nibble-swapped version, compatible
with a certain controller documented in the file header.
The drivers/Makefile would be modified to include this
driver.
Regards,
Greg
