On Thu, Dec 17, 2015 at 10:26:07AM +0100, Hans de Goede wrote:
Hi,
On 17-12-15 10:21, Ian Campbell wrote:
On Thu, 2015-12-17 at 07:40 +0100, Karsten Merker wrote:
On Thu, Dec 17, 2015 at 01:59:57PM +0900, Masahiro Yamada wrote:
2015-12-17 13:58 GMT+09:00 Masahiro Yamada <yamada.masahiro@socionext.c om>:
Hi,
I noticed some well-maintained new SoC families still define CONFIG_CMDLINE_TAG.
For example,
[...]
include/configs/sunxi-common.h
#define CONFIG_SETUP_MEMORY_TAGS #define CONFIG_CMDLINE_TAG #define CONFIG_INITRD_TAG #define CONFIG_SERIAL_TAG
Do they still use ATAGS, not device tree?
Sunxi uses devicetree for mainline kernels, but AFAIK ATAG support is necessary to enable booting legacy vendor kernels. There is still new sunxi-based hardware sold today that comes with legacy 3.4-based kernels.
That legacy kernel is FEX (allwinners own description blob) based, I don't know to what extent that involves ATAGs in some way though.
There are also people who use the 3.4 based fork from linux-sunxi.org, but I don't know if that is DT or ATAGS or FEX.
A dependency on CONFIG_OLD_SUNXI_KERNEL_COMPAT might be an option depending on what the kernels need, Hans probably knows better than I do.
The 3.4 based kernels use both ATAGS for things like memory size, and fex for other hw config info.
I'm not in favor of wrapping things in CONFIG_OLD_SUNXI_KERNEL_COMPAT, because recent 3.4 based kernels can boot without that, and I believe that removing the ATAG support will break this, without really buying us much.
+1. ATAG is also used iirc for some other operating systems, still.