[Buildroot] [PATCH 8/9] boot/syslinux: add option to install the EFI image

[Arnout Vandecappelle <arnout@mind.be>]

On 28/04/14 21:45, Yann E. MORIN wrote:
> Arnout, All,
> 
> On 2014-04-28 21:16 +0200, Arnout Vandecappelle spake thusly:
>> On 28/04/14 19:15, Yann E. MORIN wrote:
>>> Arnout, All,
>>>
>>> On 2014-04-28 08:18 +0200, Arnout Vandecappelle spake thusly:
>>>> On 25/04/14 00:30, Yann E. MORIN wrote:
>>>>> From: "Yann E. MORIN" <yann.morin.1998@free.fr>
>> [snip]
>>>>> +choice
>>>>> +	bool "Image type"
>>>>
>>>>  Why is this a choice? It's possible to build both, no? Similar to
>>>> iso/pxe. So it makes more sense to me to add efi as a third option after
>>>> iso and pxe.
>>>
>>> Well, the target will be either BIOS-based or an EFI-based, not both.
>>> So it seems more logical to make it a choice (Thomas seemed to agree on
>>> IRC, as well.)
>>>
>>> But thinking of it, we could go even further: iso/pxe/mbr/efi are all
>>> _alternate_ methods of booting, so it does not make sense to have more
>>> than one selected at any one time.
>>>
>>> The only reason pxe/iso are not a choice _currently_ (e.g. syslinux-4.0.7),
>>> is that they are always built, and there is a no way to only build one or
>>> the other. This is the same behaviour in 6.0.2: you can build any
>>> combination of {bios,efi32,efi64} (only one, two, or all of them). But
>>> bios will always build pxe and iso (and mbr, see next cset).
>>
>>  Good point. But then of course, it also doesn't make sense to build both
>> U-Boot and syslinux :-)
>>
>>  So I'm OK with making iso/pxe/mbr/efi a choice.
>>
>>  When syslinux/extlinux is added, that does add some difficulty because
>> those can be combined with mbr. But that can be tackled when the problem
>> arises :-).
> 
> Not really, because extlinux is a host tools that prepares a partition
> to be booted from the mbr blob.
> 
> Here is the way you'd use extlinux:
>   - prepare a device with at least one partition
>   - format that partition as ext2/3/4
>   - run extlinux on that partition
>      -> extlinux installs some files in that filesystem
>      -> and then installs a special boot-record as the first sector of
>         the partition (yes, the first sector of an ext2/3/4 FS is free
>         to use)
>   - dump the mbr.bin blob as the MBR (eg. on the first sector of the
>     partition)
> 
> So, we need not add an option of extlinux since it is not an image like
> pxelinux or isolinux, but really a host tool.

 Yes, of course, thanks for the explanation. Next time I'll try to think
first :-)

 Regards,
 Arnout

> 
> The addition of the mbr option in patch #9 is just so it is possible to
> indeed use extlinux.
> 
> Note: the initial patch that prompted me to write this series did try to
> install extlinux to $(IMAGE_DIR) but that's plain wrong; see:
>     http://patchwork.ozlabs.org/patch/306958/
> 
> Regards,
> Yann E. MORIN.
> 


-- 
Arnout Vandecappelle                          arnout at mind be
Senior Embedded Software Architect            +32-16-286500
Essensium/Mind                                http://www.mind.be
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