Messages in this thread | | | Date | Mon, 18 Oct 1999 15:31:26 +0300 | From | Matti Aarnio <> | Subject | Re: mm and DMA devices |
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On Mon, Oct 18, 1999 at 01:05:09PM +0200, Jens David wrote: > Greetings. > > I am the developer of a new medium speed PCI SCC card for > HDLC use (ham radio that is). The chip I use (Siemens/Infineon > DSCC-4) features busmaster DMA for transfer of data from/to > host memory. I am having some problems with buffer handling here.
You should look at any of PCI bus-master Ethernet cards, which have exactly the same problemset. ... > 1.) I will use up "expensive" below-16MB-memory which ought to be > kept for ISA-DMA applications.
Perhaps you want 'GFP_DMA32' allocations ? And if the buffer isn't in appropriate area, non-irq-space part of your driver must copy things over into appropriate area for transmit.
Such allocation space does not exist, though...
Do you *really* have more than 1 or 2 GB RAM at your box ?
> 2.) When asked by the network subsystem to transmit a buffer I can > not choose the kind of memory the data is provided in. I can only > either copy it around or take the risk it will be pulled away > under my feet.
No, data waiting for transmit won't be pulled away before your driver gives a permission for it. You are implying of giving that permission too early..
> Comments? > -- Jens
/Matti Aarnio <matti.aarnio@sonera.fi> oh2mqk
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