On Thu, Oct 07, 2021 at 02:05:41AM -0700, Zev Weiss wrote: > On Thu, Oct 07, 2021 at 12:04:41AM PDT, Andy Shevchenko wrote: > > On Thu, Oct 7, 2021 at 3:10 AM Zev Weiss <zev@xxxxxxxxxxxxxxxxx> wrote: > > > This patch series is in some ways kind of a v2 for the "Dynamic > > > aspeed-smc flash chips via 'reserved' DT status" series I posted > > > previously [0], but takes a fairly different approach suggested by Rob > > > Herring [1] and doesn't actually touch the aspeed-smc driver or > > > anything in the MTD subsystem, so I haven't marked it as such. > > > > > > To recap a bit of the context from that series, in OpenBMC there's a > > > need for certain devices (described by device-tree nodes) to be able > > > to be attached and detached at runtime (for example the SPI flash for > > > the host's firmware, which is shared between the BMC and the host but > > > can only be accessed by one or the other at a time). > > > > This seems quite dangerous. Why do you need that? > > Sometimes the host needs access to the flash (it's the host's firmware, > after all), sometimes the BMC needs access to it (e.g. to perform an > out-of-band update to the host's firmware). To achieve the latter, the > flash needs to be attached to the BMC, but that requires some careful > coordination with the host to arbitrate which one actually has access to it > (that coordination is handled by userspace, which then tells the kernel > explicitly when the flash should be attached and detached). > > What seems dangerous? > > > Why can't device tree overlays be used? > > I'm hoping to stay closer to mainline. The OpenBMC kernel has a documented > policy strongly encouraging upstream-first development: > https://github.com/openbmc/docs/blob/master/kernel-development.md > > I doubt Joel (the OpenBMC kernel maintainer) would be eager to start > carrying the DT overlay patches; I'd likewise strongly prefer to avoid > carrying them myself as additional downstream patches. Hence the attempt at > getting a solution to the problem upstream. Then why not work to get device tree overlays to be merged properly? Don't work on a half-of-a-solution when the real solution is already here. thanks, greg k-h
