Re: [Qemu-devel] [PATCH v4 1/9] ACPI: Add a function for building named qword entries

[Michael S. Tsirkin]

On Thu, Jan 26, 2017 at 07:25:22PM +0100, Laszlo Ersek wrote:
> On 01/26/17 19:15, Michael S. Tsirkin wrote:
> > On Thu, Jan 26, 2017 at 06:43:22PM +0100, Laszlo Ersek wrote:
> >> On 01/26/17 16:20, Michael S. Tsirkin wrote:
> >>> On Thu, Jan 26, 2017 at 01:48:37AM +0100, Laszlo Ersek wrote:
> >>
> >>>> But, again, I'd like to keep COMMAND_ALLOCATE_RETURN_ADDR 8-byte wide.
> >>>
> >>>
> >>> What is COMMAND_ALLOCATE_RETURN_ADDR? I'm only familiar with
> >>> COMMAND_ALLOCATE.
> >>
> >> It's a new command being introduced in this series, at my suggestion. It
> >> does the exact same thing as COMMAND_ALLOCATE, except once the
> >> allocation / download is carried out by the firmware, the firmware
> >> writes back the allocation address to the fw_cfg file that is named in
> >> an additional field of the COMMAND_ALLOCATE_RETURN_ADDR structure. (This
> >> is how QEMU learns where the blob in GPA space was placed by the
> >> firmware.) The format for this address-receiving fw_cfg file is supposed
> >> to be 8-byte, little endian.
> > 
> > I see. I really think it's better as a separate command though.
> > E.g. COMMAND_WRITE_PTR?
> 
> Sure, but please provide specifics, otherwise Ben & myself will have a
> hard time divining & implementing your intent :)
> 
> Thanks,
> Laszlo

I would say a variant of ADD_POINTER:

        /*
         * COMMAND_WRITE_POINTER - update a writeable file named
         * @pointer.dest_file at @pointer.offset, by writing pointer to
         * the table originating from @src_file. 1,2,4 or 8 byte
         * unsigned write is used depending on @pointer.size.
         */
        struct {
            char dest_file[BIOS_LINKER_LOADER_FILESZ];
            char src_file[BIOS_LINKER_LOADER_FILESZ];
            uint32_t offset;
            uint8_t size;
        } pointer;