On Mon, 8 Jun 2026 at 17:02, Philippe Mathieu-Daudé <[email protected]> wrote: > > On 8/6/26 11:12, Peter Maydell wrote: > > On Wed, 3 Jun 2026 at 08:08, Philippe Mathieu-Daudé <[email protected]> > > wrote: > >> > >> On 29/5/26 19:46, Peter Maydell wrote: > >>> The fw_cfg_init_io_dma() function allows the caller to specify the > >>> base port number of the selector/data register and the base port > >>> number of the DMA address register separately. No caller actually > >>> uses this: they all pass in base + 4 for the dma_iobase. > >>> > >>> To reduce the risk of unnecessary variation in what different x86 > >>> machine types use as their fw_cfg register layout, remove the > >>> dma_iobase argument from fw_cfg_init_io_dma(), and have the function > >>> always use the same "DMA port is base port + 4" layout. > >>> > >>> Signed-off-by: Peter Maydell <[email protected]> > >>> --- > >>> hw/i386/fw_cfg.c | 3 +-- > >>> hw/i386/microvm.c | 3 +-- > >>> hw/i386/pc.c | 3 +-- > >>> hw/nvram/fw_cfg.c | 8 ++++---- > >>> include/hw/nvram/fw_cfg.h | 17 +++++++++++++++-- > >>> 5 files changed, 22 insertions(+), 12 deletions(-) > >> > >> > >>> diff --git a/include/hw/nvram/fw_cfg.h b/include/hw/nvram/fw_cfg.h > >>> index 45a3747908..be3fb5f8aa 100644 > >>> --- a/include/hw/nvram/fw_cfg.h > >>> +++ b/include/hw/nvram/fw_cfg.h > >>> @@ -305,8 +305,21 @@ bool fw_cfg_add_file_from_generator(FWCfgState *s, > >>> Object *parent, const char *part, > >>> const char *filename, Error > >>> **errp); > >>> > >>> -FWCfgState *fw_cfg_init_io_dma(uint32_t iobase, uint32_t dma_iobase, > >>> - AddressSpace *dma_as); > >>> +/** > >>> + * fw_cfg_init_io_dma: > >>> + * @iobase: x86 port number which is the base of the fw_cfg port range > >> > >> s/x86/ISA/? > > > > This is specifically x86, because we use this where we're > > wiring fw_cfg up to the x86 in/out port instructions. There's > > no ISA-bus version of fw_cfg. Anything other than x86 should > > be using the memory-mapped fw_cfg. > > But this "x86 port number" is really a address on the ISA I/O bus. > > Maybe make explicit we want this method restricted to x86 instead?
I do, which is why I say "x86 port number". > "ISA port number which is the base of the fw_cfg port range (restricted > to x86 targets)." This seems more confusing to me because it brings ISA into it. We don't care about ISA or not ISA, we only care that this is an x86 I/O port. It happens that on the PC the x86 I/O ports can be handled by ISA cards, but it's not relevant here. In particular, the fw_cfg device is not an ISA device. thanks -- PMM
