Impact of no_lba48{_dma} = 1 ?

[Steven Scholz <steven.scholz@imc-berlin.de>]

Hi all,

on our embedded system we connected a HDD via FPGA driectly to the CPU.
And wrote a evry simple IDE driver for it. BAsicly the HDD internbal
registers are just memory mapped. No DMA is supported by the hardware.
But I think it would be capable of 48bit LBA mode (which just means setting
the HOB bit in the device control register of the HDD correctly?)

Now I wonder what the impact of setting

	hwif->no_lba48 = 1;		/* 1 = cannot do LBA48 */
	hwif->no_lba48_dma = 1;		/* 1 = cannot do LBA48 DMA */

would be.

IIUC then no_lba48 would limit the useable size to 130GB?
Will every HDD work with no_lba48 set to 1? Even those which actually
support 48bit LBA?

How about performance impact of

		if (hwif->no_lba48 || hwif->no_lba48_dma)
			hwif->rqsize = 256;
		else
			hwif->rqsize = 65536;

in ide-probe.c ?

Thanks a million for any pointers!

Steven