Messages in this thread | | | From | Benjamin Herrenschmidt <> | Subject | Re: [RFC] I/O Access Abstractions | Date | Tue, 3 Jul 2001 16:38:02 +0200 |
| |
>> I'm more concerned about having all that space mapped permanently in >> kernel virtual space. I'd prefer mapping on-demand, and that would >> require a specific ioremap for IOs. > >I have no problem with the idea of a function to indicate which I/O maps you >are and are not using. But passing resource structs around is way too heavy
Too heavy for inx/outx, I agree, but why too heavy to ioremap ? That would make a clean abstract implementation, with a semantic like "prepare this resource for use by the driver". A kind of generic ioremap for IOs, resources, and whatever another bus type may want to define, returning a token that is to be passed to readx/writex in all cases but PIO, where it's passed to inx/outx. That souds to me like the most flexible mecanism, and the small bit of overhead of passing the resource pointer is done _once_, usually at driver init.
Something like
iomap_resource(struct resource *); iounmap_resource(struct resource *);
Eventually, we can have it more fine grained in case where the driver don't need the entire resource (maybe useful for framebuffers exporting very large double-endian apertures where only one half is needed).
iomap_resource(struct resource *, unsigned long offset, unsigned long size); iounmap_resource(struct resource *, unsigned long offset, unsigned long size);
The implementation would just call ioremap/iounmap for memory type resources, and the identity for IO resources on x86. Other archs can then play whatever tricks, like placing cookies in there.
One thing I have in mind here is the ability for things like embedded that can have weird bus types, to have additional flags in the resources taken into account by iomap/unmap to locate the proper bus, or build the proper cookie that will be used by inx/outx, or define some access attributes depending on other resource flags (write combine ?).
Ben.
- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
| |