On Thu, 4 Jun 2020 at 16:16, Philippe Mathieu-Daudé <phi...@redhat.com> wrote: > On 5/25/20 10:59 PM, Peter Maydell wrote: > > What problem is this check solving? Is there some implementation > > imposed limitation or a limit within the flash header format > > that means larger sizes don't work? If so, what's the restriction? > > I am not confident maintaining virtual device with no specifications.
This isn't a virtual device, is it? The CFI spec exists and defines what these flash devices behave like. > If someone come with a datasheet for a pflash > 256MB then we can add > another commit to relax this restriction. > If someone is forced to use a >256MB and such hardware does not exist, > I'd rather have a document in docs/specs/pflash_cfi01.rst describing the > CFI fields. > > IOW this is not a hardware limitation, but a maintenance protection. > > I am worried with the recent EDK2 activity with the SBSA-ref, and I > don't want to give false hope to developers that they can create any > kind of pflash with the current device model. > > If I reword this better in the commit description, is my argument > acceptable? Not really; I think we should know what we're limiting against. Currently you're checking total_len, but this is just sector_len * nb_blocs, so if there's a problem with silly large values then it's probably actually a problem with one of those being over-sized which would still show up even if the total_len was less than 256MB. (I suspect the underlying limit here is what the cfi_table entries 0x2D..0x30 impose on blocks_per_device and sector_len_per_device.) thanks -- PMM
