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From: "Linux  PPC" <linuxppc@rediffmail.com>
To: linux-fbdev-devel@lists.sourceforge.net
Subject: bits_per_pixel query
Date: 8 Sep 2002 16:39:36 -0000	[thread overview]
Message-ID: <20020908163936.31266.qmail@webmail30.rediffmail.com> (raw)

Hello there,

I had some doubts regarding the framebuffer struct
usage.

As I understand, the buffer is at fb_info.screen_base
and the size of the buffer is (hres * vres *
bits_per_pixel )/8. The state of the pixel at
location (x,y), would be represented by the value of
byte at screen_base + ((y*hres + x) * bits_per_pixel)/8.

If the display is 8 bit, then it would require only
a byte to represent the value of the pixel. If it were 24 bit, 
then it would require 3 bytes, and so
on. Is that right? What would happen, to the size required for the 
buffer, if the display
requires, say 12 bits per pixel, or 18 bits?

So, if I were to set all the bytes after screen_base
uptil screen_base + (hres*vres*bits_per_pixel/8) to
zeros, then I would get a black screen. Is that right?

I'm asking cos, I'm workin on a framebuffer support
for an LCD panel, and am making the above assumption
which doesn't seem happening.

- navin.

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             reply	other threads:[~2002-09-08 16:40 UTC|newest]

Thread overview: 2+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2002-09-08 16:39 Linux  PPC [this message]
2002-09-09 14:23 ` bits_per_pixel query Antonino Daplas

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