how to configure the x-win

Inky Lung ilung at
Wed Jul 5 20:28:42 PDT 2006

Hello, Alan,

thanks for your suggestion and indeed, my situation is, i have a 16 gray 
scale TFT LCD (640 x 480) connected with an ARM 9 processor and each time 
the ARM 9 processor will send out 16-bit data (RGB565) to the LCD. but, it 
will just accept R[4..1], G[5..2] & B[4..1] and drop R0, G1, G0 & B0. the 
RGB actually is repsonding to 3 pixels of the LCD, traditionally or 
normally, this refers to a single pixel in a color LCD panel. thus, here 
comes my problem, at the moment, i configure the resolution of X to 214 x 
480. and everything displayed on LCD now is 3 times wider than what the 
actual thing is. this can be expected as the LCD receives 3 pixel at the 
time. so, i'm not quite sure if i should
1. stay with depth=16 and use shadowfb to pack a 640x480 data into a 214x480 
data. or,
2. use depth=4 and relocate the data from 1111 2222 3333 4444 to 1111 x222 
2xx3 333x where x is dummy bit. and configure x to 640x480.
or if there's any way that is more straight forward?

Best regards,
Inky Lung

----- Original Message ----- 
From: "Alan Cox" <alan at>
To: "Inky Lung" <ilung at>
Cc: <xorg at>
Sent: Tuesday, July 04, 2006 8:37 PM
Subject: Re: how to configure the x-win

> Ar Maw, 2006-07-04 am 19:49 +0800, ysgrifennodd Inky Lung:
>>i have a 16 gray scaled (4bpp) TFT VGA LCD connected with an ARM 9
> processor. everything works fine on the hardware side but i got a
> headache when i tried to load and display the x-win in the LCD. so, does
> x-win supports 4bpp?
> Indirectly it will support any format by writing a shadowfb driver.
> Directly it supports a fair range including 4bpp StaticGray and
> GrayScale which sounds like what you are describing. (4bit packed pixel)
> The frame buffer mode driver does not however support 4bpp modes at the
> moment.
> Alan

More information about the xorg mailing list