Re: [OpenBIOS] VESA & DMA

[Clive Jenkins]

Your DMA code only works for channel=0,1,2,3 because the array dmaino[]
is declared with only 4 elements. When channel>=4 you are indexing
beyond the end of the array and reading whatever data happens to be next
in memory.

Good luck with the VESA problems.

Clive Jenkins.

Petazzoni Thomas wrote:
> Hi everybody,
>
> This has not much to do with the OpenBIOS project, but with low level
> programming. Everyone here seems to know lot of things in this domain,
> that's why i'm asking to all of u those questions :
> Can we setup a VESA 2 (not VESA 3 !) configuration (select video
>
> mode, and everything) without making a int 0x10 ? We're programming a
> protected mode OS, and switching to VM86 sucks. I know it's possible
> with VESA 3, but with VESA 2 ?
> If yes, do you have any docs about it ?
> Is the int 0x10 VESA code specific to each graphic card ?
> I've got a problem with DMA programming, here's my source :
>
> const static DmaChannel dmainfo[] = {
>   { 0x87, 0x00, 0x01 },
>   { 0x83, 0x02, 0x03 },
>   { 0x81, 0x04, 0x05 },
>   { 0x82, 0x06, 0x07 }
> };
>
> void dma_transfer(int channel, long physical_address, unsigned int
> length, unsigned sh
> ort read) {
>
> long page, offset;
>
> if(channel >= 4)
>    {
>      printk("\nThis function does to manage with channel 4, 5, 6, 7");
>      return ;
>    }
>
> page = physical_address >> 16;
>   offset = physical_address & 0xFFFF;
>   length -= 1;
>
> // DIsable IRQs
>   outb(0xFF, 0x21);
>   outb(0xFF, 0xA1);
>
> // Masking channel (disable)
>   outb(channel | 4, 0x0A);
>
> // Reset Flip-Flop
>   outb(0, 0xC0);
>
> // Mode
>   outb( (read ? 0x48 : 0x44) | channel, 0x0B);
>
> // Page
>   outb(page, dmainfo[channel].page);
>
> // Offset
>   outb(offset & 0xFF, dmainfo[channel].offset);
>   outb((offset >> 8) & 0xFF, dmainfo[channel].offset);
>
> // Length
>   outb(length & 0xFF, dmainfo[channel].length);
>   outb((length >> 8) & 0xFF, dmainfo[channel].length);
>
> // Unmask
>   outb(channel, 0x0A);
>
> // Enabling IRQs
>   outb(0, 0x21);
>   outb(0, 0xA1);
>
> }
>
> I use it to transfer a sector from the floppy disk. Do you see anything
> wrong in this code ?
> The transfer is not made by the floppy, and i don't know why...
> I don't know if it's in the DMA programming, or in the floppy driver
> ..............
>
> Help !
>
> Thanks,
>
> Thomas, from france
>
> (If you speak french, you can join the KOS project :
> http://kos.enix.org)
>
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