Date: Wed, 7 Jul 1999 14:40:13 -0500 (CDT) From: Jonathan Lemon <jlemon@americantv.com> To: hm@kts.org, hackers@freebsd.org Subject: Re: howto allocate 32k phys. mem-space in driver ? Message-ID: <199907071940.OAA28900@free.pcs> In-Reply-To: <local.mail.freebsd-hackers/m111mgq-00002VC@bert.kts.org>
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In article <local.mail.freebsd-hackers/m111mgq-00002VC@bert.kts.org> you write:
>Hi,
>
>perhaps i don't see the wood for trees.
>
>I'd like to write a driver for a PCI ISDN chipset which uses a 32k byte
>memory window as a sort of "dual ported ram" in the memory address space.
>
>What has to be done in the driver attach routine is
>
> - allocate a 32k contingous memory window
> - get the physical address of it
> - program the ISDN PCI chipset with the start address of the window
>
>Now can i just malloc 32k and then use vtophys() to get the physical
>start address to program the PCI chip with ?
With the "new-bus" architecture, I believe this is done the following way:
1. Create a DMA tag describing the amount of memory needed, and what
the alignment constraints are.
error = bus_dma_tag_create( .... );
2. Allocate the memory described by the tag.
error = bus_dmamem_alloc( .... );
3. Map the memory into the address space. A callback routine is used
to record the physical -> virtual mapping.
bus_dmamap_load( .... );
For pre-newbus, I think you just call contigmalloc(), and vtophys().
--
Jonathan
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