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[Qemu-devel] Re: [PATCHv4 15/15] Pass boot device list to firmware.


From: Kevin O'Connor
Subject: [Qemu-devel] Re: [PATCHv4 15/15] Pass boot device list to firmware.
Date: Mon, 15 Nov 2010 21:52:19 -0500
User-agent: Mutt/1.5.21 (2010-09-15)

On Mon, Nov 15, 2010 at 03:36:25PM +0200, Gleb Natapov wrote:
> On Mon, Nov 15, 2010 at 08:26:35AM -0500, Kevin O'Connor wrote:
> > On Mon, Nov 15, 2010 at 09:40:08AM +0200, Gleb Natapov wrote:
> > > On Sun, Nov 14, 2010 at 10:40:33PM -0500, Kevin O'Connor wrote:
> > > > Why not just return a newline separated list that is null terminated?
> > > > 
> > > Doing it like this will needlessly complicate firmware side. How do you
> > > know how much memory to allocate before reading device list?
> > 
> > My preference would be for the size to be exposed via the
> > QEMU_CFG_FILE_DIR selector.  (My preference would be for all objects
> > in fw_cfg to have entries in QEMU_CFG_FILE_DIR describing their size
> > in a reliable manner.)
> > 
> Will interface suggested by Blue will be good for you? The one with two
> fw_cfg ids. BOOTINDEX_LEN for len and BOOTINDEX_DATA for device list. I

I dislike how different fw_cfg objects pass the length in different
ways (eg, QEMU_CFG_E820_TABLE passes length as first 4 bytes).  This
is a common problem - I'd prefer if we could adopt one uniform way of
passing length.  I think QEMU_CFG_FILE_DIR solves this problem well.

I also have an ulterior motive here.  If the boot order is exposed as
a newline separated list via an entry in QEMU_CFG_FILE_DIR, then this
becomes free for coreboot users as well.  (On coreboot, the boot order
could be placed in a "file" in flash with no change to the seabios
code.)

-Kevin



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