[U-Boot] [PATCH v2 06/26] dm: core: Allocate platform data when binding a device

[Masahiro YAMADA]

Hi Simon,


2015-01-24 0:50 GMT+09:00 Simon Glass <sjg at chromium.org>:

>
> I tried to document the reasoning in the patches, but let me try to
> expand a bit. Hopefully this can provoke further comments /
> improvements.
>
> The main motivation for me was that buses want to set up the platform
> data for their children before they are probed. In fact some children
> may never be probed. For example a SPI bus wants to know the chip
> select for each of its children.
>
> At present we have to hunt around in the device tree to figure out
> which child is the right one, so we can probe it. Worse, the
> children's drivers (e.g. cros_ec on a SPI bus) have to be involved in
> setting themselves up. The device_probe_child() function was my
> attempt to make this fit better, and it did work, but I was not happy
> with it. You can see that from my unhappy comments in cros_ec, or SPI
> flash probe, for example.
>
> The new approach makes buses easier to deal with as I hope you can
> see. The 'bind' step is supposed to set up the entire basic framework
> of the drivers at start-up. Everything should be visible in the tree
> (the exception being buses which must be probed at run-time) but
> nothing should be probed. Now, we are following that approach for
> buses also.

OK.
I understand that this concept makes things much simpler, so

Reviewed-by: Masahiro Yamada <yamada.m at jp.panasonic.com>


Perhaps, we can have a flag like DM_FLAG_ALLOC_PLATDATA_LATE:
 If this flag is set, platdata is allocated in device_probe(), not
device_bind().
But, I think it might make things much more complicated and
probably make you unhappy.
I do not have a strong option about this.


Let's go with your idea!
If something does not go well, then we can come back here.




> Re the disadvantages:
>
> - the per-child platform data for a bus is small, and we need not bind
> devices which are disabled. So, a board should avoid having a lot of
> enabled devices which are never used
> - malloc() is very fast, it is the platform data setup that takes
> time. I agree this slows things down. But currently it only affects
> bus children, and only their basic information such as chip select.
>
> The use of ofdata_to_platdata() is stil confined to when the device is
> actually probed. This helps to keep things fast in the common case
> where we don't need the platform data earlier.
>
> I think we can refine this further, but what I have now feels a lot
> cleaner to me.

OK!



I have done with a quick review of this series.

I left some comments on some patches,but they are all minor issues.

If you agree to fix them, please send v3.
I am OK with the whole concept, so I guess we can get it in during  this MW.

Thanks!




-- 
Best Regards
Masahiro Yamada