On Wed, Jun 01, 2016 at 05:41:53PM +0200, Arnd Bergmann wrote: > On Wednesday, June 1, 2016 10:09:29 AM CEST Bjorn Helgaas wrote: > > Hi Arnd, > > > > On Wed, Jun 01, 2016 at 02:31:22PM +0200, Arnd Bergmann wrote: > > > A lot of PCI host bridges require different methods for initiating > > > type 0 and type 1 config space accesses, leading to duplication of > > > code. > > > > > > This adds support for the two different kinds at the pci_ops > > > level, with the newly added map_bridge/read_bridge/write_bridge > > > operations for type 1 accesses. > > > > > > When these are not set, we fall back to the regular map_bus/read/write > > > operations, so all existing drivers keep working, and bridges that > > > have identical operations continue to only require one set. > > > > This adds new config accessor functions to struct pci_ops and makes > > the callers responsible for figuring out which one to use. The > > benefit is to reduce code duplication in some host bridge drivers > > (DesignWare and MVEBU so far). > > > > From a design perspective, I'm not comfortable with moving this burden > > from the host bridge drivers to the callers of the config accessors. > ... > Maybe we can simply change them to use the normal API and come up with > a way to make the pci_ops harder to misuse? Would it make you feel better > if we also renamed .read/.write into .read_type0/.write_type0 or something > like that? I'm trying to get a better feel for the tradeoff here. It seems like an API complication vs. code duplication. I don't really think the callers should have to figure out which accessor to use. How much of a benefit do we really gain by complicating the callers? We've managed for quite a few years with the current scheme, and it seems like only a couple new ARM platforms would benefit. Bjorn -- To unsubscribe from this list: send the line "unsubscribe linux-pci" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
