On Fri, Jan 27, 2017 at 10:43:13AM -0500, Kevin O'Connor wrote: > On Fri, Jan 27, 2017 at 03:46:33PM +0100, Laszlo Ersek wrote: > > On 01/27/17 15:18, Kevin O'Connor wrote: > > > If an offset is going to be added, shouldn't both a source offset and > > > destination offset be used? > > > > > > /* > > > * COMMAND_WRITE_POINTER - update a writeable file named > > > * @pointer.dest_file at @pointer.dest_offset, by writing pointer > > > * plus @pointer.src_offset to the blob 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 src_offset, dest_offset; > > > uint8_t size; > > > } pointer; > > > > > > I doubt the offsets or size is really all that important though. > > > > The offset into the fw_cfg file that receives the allocation address is > > important, that allows the same file to receive several different > > addresses (for different downloaded blobs), at different offsets. > > > > OTOH, asking the firmware to add a constant to the address value before > > writing it to the fw_cfg file is not necessary, in my opinion. The blob > > that the firmware allocated and downloaded originates from QEMU to begin > > with, so QEMU knows its internal structure. > > I guess I'm missing why QEMU would want to use the same writable file > for multiple pointers as well as why it would want support for > pointers smaller than 8 bytes in size. If it's because it may be > easier to support an internal QEMU blob of a particular format, then > adding a src_offset would facilitate that. > > However, if it was done so that WRITE_POINTER mimicks ADD_POINTER then > that's fine too. I'm okay with either format. > > -Kevin
Both reasons :) offset is because it's easier for QEMU not to have to add more files (e.g. it simplifies cross-version migration if we don't). size is to mimick ADD_POINTER. -- MST