Messages in this thread | | | Date | Wed, 15 Aug 2001 15:10:52 +0200 | From | Jens Axboe <> | Subject | Re: [patch] zero-bounce highmem I/O |
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On Wed, Aug 15 2001, David S. Miller wrote: > From: Jens Axboe <axboe@suse.de> > Date: Wed, 15 Aug 2001 14:07:40 +0200 > > Ok so you just want to turn scatterlist into what I call sg_list in 2.5 > time, fine with me too. Depends on whether we want to keep the > pci_map_sg and struct scatterlist interface intact, or just break it and > tell driver authors they must fix their stuff regardless of whether they > want to support highmem. As I write this sentence, it's clear to me > which way is the superior :-) > > pci_map_sg is pci_map_sg, if the internal representation of > scatterlist is changed such that address/alt_address no longer exist, > it will work on pages only. Right? The compatibility mode in
Yes, the pci_* was not my worry. It's the *address case you list below, but I think you are right that it' not a big issue at that.
> 2.4.x is the "if (address != NULL) virt_to_bus(address);" stuff.
Yes, aka the horrible hack.
> Understand that the pci64_{map,unmap}_sg is created for a seperate > purpose, independant of whether scatterlist has the backwards > compatability stuff or not. (There have been threads here about this, > I can describe it quickly for you in quiet if you want to know).
I've read these now, been behind on traffic lately.
> Two more things to consider: > > 1) There is nobody who cannot be search&replace converted from > sg->address = ptr > into > sg->page = virt_to_page(ptr) > sg->offset = ((unsigned long)ptr & ~PAGE_MASK); > > The only truly problematic area is the alt_address thing. > It is would be a nice thing to rip this eyesore out of the scsi > layer anyways.
The SCSI issue was exactly what was on my mind, and is indeed the reason why I didn't go all the way and did a complete conversion there. The SCSI layer is _not_ very clean in this regard, didn't exactly enjoy this part of the work...
> 2) I want to put scatterlist in to replace skb_frag_struct in skbuff.h > and then have a zerocopy network driver do something like: > > header_dma = pci_map_single(pdev, skb->data, skb->len, PCI_DMA_TODEVICE); > data_nents = pci_map_sg(pdev, skb_shinfo(skb)->frag_list, > skb_shinfo(skb)->nr_frags, > PCI_DMA_TODEVICE); > > See? :-)
Yep, I see where you are going :)
> Yep. Want me to add in the x86 parts of your patch? > > Please let me finish up my prototype with sparc64 building and > working, then I'll send you what I have ok?
Fine
-- Jens Axboe
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