On 14.09.18 17:46, Simon Glass wrote: > Hi Alex, > > On 26 August 2018 at 19:11, Alexander Graf <ag...@suse.de> wrote: >> >> >> On 08.08.18 11:54, Simon Glass wrote: >>> At present map_sysmem() maps an address into the sandbox RAM buffer, >>> return a pointer, while map_to_sysmem() goes the other way. >>> >>> The mapping is currently just 1:1 since a case was not found where a more >>> flexible mapping was needed. PCI does have a separate and more complex >>> mapping, but uses its own mechanism. >>> >>> However this arrange cannot handle one important case, which is where a >>> test declares a stack variable and passes a pointer to it into a U-Boot >>> function which uses map_to_sysmem() to turn it into a address. Since the >>> pointer is not inside emulated DRAM, this will fail. >>> >>> Add a mapping feature which can handle any such pointer, mapping it to a >>> simple tag value which can be passed around in U-Boot as an address. >>> >>> Signed-off-by: Simon Glass <s...@chromium.org> >> >> I think you are aware that this logic will fall apart spectacularly if >> any arithmetic operation happens on the virtual (U-Boot) address, right? >> So simple code like >> >> readl(vaddr + 1); >> >> will just fail (hopefully) or (more likely) return a completely >> incorrect value. >> >> I assume this is intentional, but shouldn't the tag increment be >> something slightly larger then? > > What do you expect readl() to do on sandbox? At present it is just a > no-op. I suppose we could support memory-mapped I/O but it has not > been attempted yet.
It was really just meant as an arbitrary example of something where you assume "address + 1" == "pointer(address) + 1". Alex _______________________________________________ U-Boot mailing list U-Boot@lists.denx.de https://lists.denx.de/listinfo/u-boot
