Re: [Qemu-devel] [PATCH qemu] fdc: Exit if ISA controller does not support DMA

[Philippe Mathieu-Daudé]

On 10/26/2017 03:46 AM, Alexey Kardashevskiy wrote:
> A "powernv" machine type defines an ISA bus but it does not add any
> DMA
> controller to it so it is possible to hit assert(fdctrl->dma) by
> adding "-machine powernv -device isa-fdc".

The same happens with the Alpha machine.

On 12/13/2017 03:19 AM, Hervé Poussineau wrote:
> Le 08/12/2017 à 22:29, John Snow a écrit :
> [...]
>>
>> It looks like Herve was working on decoupling floppies from i8257, but
>> perhaps didn't get all the way through -- I'm not actually clear on what
>> work remains to be done here, maybe he can chime in if he's still
>> interested in the project?
>>
> 
> Indeed, I worked on decoupling floppies (and other ISA devices) from
> i8257, for three reasons:
> 1) having a working floppy on MIPS Magnum machine. fdc is PC-compatible,
> but DMA controller is not i8257-compatible.
> 2) reimplement another ISA bus with a somewhat i8257-compatible DMA
> 3) for fun, support multiple ISA buses on a same machine but on
> different PCI bridges.
> 
> I failed on point 1), mostly due to lack of documentation.
> I succeeded on point 2), by having locally some patches for a ISAPNP
> bus, where IO/IRQ/DMA addresses of ISA devices can change dynamically,
> and devices can be discovered by operating system.
> About point 3, most of the patches are ready, but some details are still
> to be fixed.

I'm having hard time refactoring all these PC chipsets, I'll make some
room to send my current work as RFC before soft freeze.

Regards,

Phil.