[U-Boot] Displaying characters on the display in u-boot

[Bhargav A K]

Hi Anatolij

Thank you very much for Ur guidance

> What U-Boot version do you use?

U-Boot 1.1.4-geb3fa991 (Feb 21 2013 - 10:11:04)
(output of version command)

> This video_set_lut() function is only needed if you use 8 bits per
> pixel frame buffer.

So can I comment it out, (or) just make a dummy call and dummy return from it.
It wont affect my character(text) rendering on the display, correct ?

My last question, the board_video_init() function just initializes the board in
display/video mode. For example if I have a GPIO to switch b/w command and video
modes and a GPIO to switch on the LCD, etc., I'll have to do all such functions in it.

But if all of those are already done, I can just return a dummy from the function ?

Kind regards
Bhargav
________________________________________
From: Anatolij Gustschin [agust at denx.de]
Sent: Wednesday, March 27, 2013 8:30 PM
To: Bhargav A K
Cc: u-boot at lists.denx.de
Subject: Re: [U-Boot] Displaying characters on the display in u-boot

Hi,

please keep the U-Boot list address on Cc, other users may
find the discussion helpful.

On Wed, 27 Mar 2013 19:40:33 +0530
Bhargav A K <bhargav.ak at sasken.com> wrote:
...
> Now I will have to define video_set_lut() also, isn't it ?

It depends. What U-Boot version do you use? If you use mainline
U-Boot recent versions like v2013.01.01, then this function
already exists as a week default empty function. You do not always
need video_set_lut() functionality unless you want to use a frame
buffer configuration with 8 bits per pixel colour depth.

> Can I please get more information on what I have to handle inside the function ?

This video_set_lut() function is only needed if you use 8 bits per
pixel frame buffer. I doubt that you want to use it since the
splash screen quality will be really bad in this color depth mode.
If you want to use this depth, then this function should fill the
color palette (look up table) of the display controller using the
index argument of the function as an index into look-up table and
using other arguments as values for the look-up table entries
under that index.

> Also, Is there any place where I can of getting more information on the structure members
> of "struct GraphicDevice" ?

the needed struct members are more or less self-explanatory, so
these are not documented anywhere, I think. You need to init
only:

 winSizeX  - the width of the display in pixels
 winSizeY  - the height of the display in pixels
 gdfBytesPP - frame buffer color depth in bytes per pixel
 gdfIndex   - graphics data format of the frame buffer,
              it is one of
               GDF__8BIT_INDEX
               GDF_15BIT_555RGB
               GDF_16BIT_565RGB
               GDF_32BIT_X888RGB
               GDF_24BIT_888RGB
               GDF__8BIT_332RGB

 frameAdrs - the starting frame buffer address in the video ram

You do not need to initialise other members.

Thanks,

Anatolij

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