We originally implemented '-machine dumpdtb' in a fairly ad-hoc way: every machine using FDT is supposed to call qemu_fdt_dumpdtb() once it has finished creating and modifying the DTB; if the user passed in the machine option then qemu_fdt_dumpdtb() will write the FDT to a file and then exit QEMU.
Somewhat later we implemented the QMP and HMP dumpdtb commands; for these to work we had to make all the FDT-using machines set MachineState::fdt to point to the FDT blob. This means we can clean up the handling of the -machine option, so we can implement it in one place in machine.c. The benefit of this is: * boards only need to do one thing, not two * we can have better error messages for the "user asked us to dump the DTB but this board doesn't have one" case (In particular the bug report https://gitlab.com/qemu-project/qemu/-/issues/2733 is essentially because we silently ignore the option if there is no DTB to dump.) The openrisc machines and the MIPS boston machine both were not setting MachineState::fdt, so the HMP/QMP dumpdtb don't work for those machines; the series starts by fixing those bugs. Then we can implement the centralized handling of the machine option. Finally we get to fix the "no error message" problem: $ qemu-system-aarch64 -M raspi4b,dumpdtb=/tmp/d.dtb qemu-system-aarch64: This machine doesn't have an FDT (Perhaps it doesn't support FDT at all, or perhaps you need to provide an FDT with the -fdt option?) The fact that there are three places that report "this machine doesn't have an FDT" is a bit of a wart, stemming largely from the fact that the QMP dumpdtb command is only conditionally present if CONFIG_FDT. In theory we could make it unconditional, but I opted to leave that can of worms for another day... thanks -- PMM Peter Maydell (6): monitor/hmp-cmds.c: Clean up hmp_dumpdtb printf hw/openrisc: Support monitor dumpdtb command hw/mips/boston: Check for error return from boston_fdt_filter() hw/mips/boston: Support dumpdtb monitor commands hw: Centralize handling of -machine dumpdtb option hw/core/machine.c: Make -machine dumpdtb=file.dtb with no DTB an error include/hw/loader-fit.h | 21 +++++++++++++++++--- include/hw/openrisc/boot.h | 3 ++- include/system/device_tree.h | 2 -- hw/arm/boot.c | 2 -- hw/core/loader-fit.c | 38 ++++++++++++++++++++---------------- hw/core/machine.c | 23 ++++++++++++++++++++++ hw/loongarch/virt.c | 1 - hw/mips/boston.c | 16 ++++++++++----- hw/openrisc/boot.c | 8 +++++--- hw/openrisc/openrisc_sim.c | 2 +- hw/openrisc/virt.c | 2 +- hw/ppc/e500.c | 1 - hw/ppc/pegasos2.c | 1 - hw/ppc/pnv.c | 1 - hw/ppc/spapr.c | 1 - hw/riscv/boot.c | 2 -- monitor/hmp-cmds.c | 2 +- system/device_tree-stub.c | 5 ++++- system/device_tree.c | 22 ++++++--------------- 19 files changed, 93 insertions(+), 60 deletions(-) -- 2.34.1
