Video memory mapping - HOWTO?

NTDEV
1

Hello

I’m trying to map the video memory in order to display text from a
boot driver. i know the memory for color display starts at 0xA0000 but
for some reason this isn’t working:

#define BUFFERSIZE 8192
PHYSICAL_ADDRESS paVideoMem;
PUCHAR pVideoMem = NULL;

paVideoMem.LowPart = 0xA0000;
pVideoMem = MmMapIoSpace(paVideoMem,BUFFERSIZE,FALSE);
*pVideoMem = 0x07690748 // should print H in the upper left corner

Any suggestions ?

Thanx.

2

1, Are you sure that your video card is actually mapped at A0000? In
WinDBG, do a “!pci 1 1” to see what the base address of the card is. You
want “BAR 1” address, as this is video memory. BAR 0 is usually the control
region, which you don’t want to touch. You could also use something like
“!dd [uc] a0000” or “!ed [uc] a0000 07690748” to test if the physical
address is actually your graphics card.

  1. Is the code below complete, i.e. do you not set the “highpart” of the
    memory address to zero? If not, it may map a different (or no) region of
    memory.

But more importantly, why? You should be able to use the following
technique (from e-mail by Maxim S. Shatskih):
InbvEnableDisplayString(TRUE) switches the screen to a mode where
string
can be displayed, the ZwDisplayString(PUNICODE_STRING) displays a string.

And your poke of the screen should display “Hi” in light grey, by the way.

I hope you don’t plan to do this in a production driver. At least not
without thorough error checking, so as to avoid problems where there is no
graphics card available in the machine.

–
Mats

Hello

I’m trying to map the video memory in order to display text from a
boot driver. i know the memory for color display starts at 0xA0000 but
for some reason this isn’t working:

#define BUFFERSIZE 8192
PHYSICAL_ADDRESS paVideoMem;
PUCHAR pVideoMem = NULL;

paVideoMem.LowPart = 0xA0000;
pVideoMem = MmMapIoSpace(paVideoMem,BUFFERSIZE,FALSE);
*pVideoMem = 0x07690748 // should print H in the upper left corner

Any suggestions ?

Thanx.

Questions? First check the Kernel Driver FAQ at http://www.
osronline.com/article.cfm?id=256

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3

(1) Be in VGA mode to see this memory mapped.
(2) Or go to a does full screen and go to a VGA mode to see this mapped.
(3) These are done thru the miniport.
(4) For a Super VGA mode the miniport will do VideoPortMapMemory() when
DirectDraw wants the Virutal Address of the Framebuffer.

Thanks
Mike Jones

“Sharon Sahar” wrote in message news:xxxxx@ntdev…
> Hello
>
> I’m trying to map the video memory in order to display text from a
> boot driver. i know the memory for color display starts at 0xA0000 but
> for some reason this isn’t working:
>
> #define BUFFERSIZE 8192
> PHYSICAL_ADDRESS paVideoMem;
> PUCHAR pVideoMem = NULL;
>
> paVideoMem.LowPart = 0xA0000;
> pVideoMem = MmMapIoSpace(paVideoMem,BUFFERSIZE,FALSE);
> *pVideoMem = 0x07690748 // should print H in the upper left corner
>
> Any suggestions ?
>
> Thanx.
>

4

I think the original poster wanted to do this BEFORE the display driver and
relevant miniport is loaded. Otherwise it doesn’t make much sense.

–
Mats
xxxxx@lists.osr.com wrote on 02/15/2005 03:21:57 PM:

(1) Be in VGA mode to see this memory mapped.
(2) Or go to a does full screen and go to a VGA mode to see this mapped.
(3) These are done thru the miniport.
(4) For a Super VGA mode the miniport will do VideoPortMapMemory() when
DirectDraw wants the Virutal Address of the Framebuffer.

Thanks
Mike Jones

“Sharon Sahar” wrote in message
news:xxxxx@ntdev…
> > Hello
> >
> > I’m trying to map the video memory in order to display text from a
> > boot driver. i know the memory for color display starts at 0xA0000 but
> > for some reason this isn’t working:
> >
> > #define BUFFERSIZE 8192
> > PHYSICAL_ADDRESS paVideoMem;
> > PUCHAR pVideoMem = NULL;
> >
> > paVideoMem.LowPart = 0xA0000;
> > pVideoMem = MmMapIoSpace(paVideoMem,BUFFERSIZE,FALSE);
> > *pVideoMem = 0x07690748 // should print H in the upper left corner
> >
> > Any suggestions ?
> >
> > Thanx.
> >
>
>
>
> —
> Questions? First check the Kernel Driver FAQ at http://www.
> osronline.com/article.cfm?id=256
>
> You are currently subscribed to ntdev as: xxxxx@3dlabs.com
> To unsubscribe send a blank email to xxxxx@lists.osr.com

> ForwardSourceID:NT0000CFFE