On 5/13/21 2:23 PM, Peter Maydell wrote: > On Thu, 13 May 2021 at 12:49, Jonathan Cameron > <jonathan.came...@huawei.com> wrote: >> My initial suggestion was to fix this by adding the relatively >> simple code needed in the driver to implement byte read / write, >> but Ben pointed at the QEMU docs - docs/devel/memory.rst which >> says >> " >> .impl.min_access_size, .impl.max_access_size define the access sizes >> (in bytes) supported by the *implementation*; other access sizes will be >> emulated using the ones available. For example a 4-byte write will be >> emulated using four 1-byte writes, if .impl.max_access_size = 1. >> " >> >> This isn't true when we have the situation where >> .valid.min_access_size < .imp.min_access_size >> >> So change the docs or try to make this work?
See also this patch from Francisco: https://www.mail-archive.com/qemu-devel@nongnu.org/msg636935.html And full unaligned access support from Andrew: https://www.mail-archive.com/qemu-devel@nongnu.org/msg461247.html > I don't (yet) have a view on what the in-principle right thing > should be, but in practice: how many devices do we have which > set .valid.min_access_size < .imp.min_access_size ? If we want > to change the semantics we'd need to look at those to see if they > need to be adjusted (or if they're just currently buggy and would > be fixed by the change). > > thanks > -- PMM >
