Re: [PATCH 2/2] sdhci-pxa: add call back interface to share sdhci-pxa

[Arnd Bergmann <arnd@arndb.de>]

On Thursday 19 May 2011, zhangfei gao wrote:
> To make sdhci-pxa easy to maintain, we still prefer put platform
> specific difference under platform code.
> 
> "Identify controller from platform data" looks to me is same as using #ifdef.
> The method is used in our another driver before.

I meant run-time code, not compile-time #ifdef. In the long run, we
want to have a kernel that is able to work on many different systems,
and that means the drivers should not impose hardcoded limitations.

> More and more workaround comes when more and more platform need to
> support, making the driver bigger and bigger and not easy to maintain.
> Nobody remember what's the workaround purpose several years later.
> So the result is we have to re-write the driver again to make it simple :(
> 
> Currently, the ip is shared among mmp2, pxa910, pxa168 etc, pxa910
> maintainer does not care what workaround is used on pxa168.
> When mmp3 wants to reuse the ip, it's easier to not care what's the
> history at all.
> 
> So we still prefer keep driver as simple as possible, while specific
> platform self-maintain specific workaround , which is not aware to
> other platform.

There are a lot of different ways to do the same thing, but splitting
out code into the subarchitecture is not a good one. Please have a look
at how Shawn Guo has reworked the sdhci-pltfm drivers to have common
part as a library and then multiple users of that. You can probably
do the same with the different versions of the sdhci-pxa driver.

	Arnd