Re: Does kmalloc always return address below 4GB?

[Gerd Knorr <kraxel@bytesex.org>]

> >Look at other drivers using the DMA interfaces like the two aic7xxx
> >and all of the sym53c8xx drivers, they get it right.
>  
>  	Grepping for vmalloc and kmap in them turns up no hits.

Why do you want to vmalloc() memory in the scsi driver?

>  computer with >4GB of RAM (CONFIG_HIGHEM) talking to a PCI card
>  that only does 32-bit addressing:
>  
>  		pci_set_dma_mask(pcidev, 0xffffffff);
>  		addr = vmalloc(nbytes);
>  		/* On an x86 with >4GB of RAM, addr will be <4GB, but
>  	           __pa(addr) might be >4GB, and the system lacks
>  	           PCI address mapping harware. */

use vmalloc_32(), this one returns lowmem.

>  		dma_addr = pci_map_single(pcidev, addr, nbytes, direction);

This is illegal because addr is a kernel _virtual_ address.  You have to
get the page using vmalloc_to_page() and feed this to pci_map_page()
then.  With nbytes > PAGE_SIZE you probably want to build a scatterlist
and use pci_map_sg().

  Gerd

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