Re: [PATCHv2] Add dynamic video initialization to barebox

[Sascha Hauer <s.hauer@pengutronix.de>]

On Mon, Nov 15, 2010 at 10:57:01AM +0100, Juergen Beisert wrote:
> Hi Sascha,
> 
> Sascha Hauer wrote:
> > On Tue, Oct 26, 2010 at 01:31:36PM +0200, Juergen Beisert wrote:
> > > Currently barebox uses a fixed videomode setup. Everything is compiled
> > > in. This change adds the possibility to select a videomode according to a
> > > connected display at runtime. The current behaviour is still present if
> > > not otherwise configured. If configured for runtime setup, initialization
> > > of the video hardware will be delayed until the required videomode will
> > > be selected from the shell code. If more than one videomode is supported
> > > by the platform, running the 'devinfo' command on the framebuffer device
> > > shows the supported videomode list. After selecting the videomode, the
> > > output can be enabled.
> >
> > General remarks about this series:
> >
> > - Please do not add code with '#if 0' and activate it later. This shows
> >   the series has the wrong order.
> 
> This was for review only. If I would change the code in one step, the patch is 
> unreadable.
> 
> > - Please refrain from basing your internal functions around 'struct
> >   device_d'. By doing so we completey lose type safety and at least in
> >   case of the mci framework where three different devices are involved
> >   this leads to unreadable and error prone code.
> 
> But IMHO in the case of the MCI there _are_ three devices!
>  - The one that knows how to handle disk drives
>  - The one that knows what a SD card is
>  - the one that knows how to transfer data from an to an attached device.
> 
> Why this is unreadable or error prone? If you combine all these different 
> functions into one I would say: Yes, the result is unreadable and error 
> prone. And if you would say for a bootloader this separate approach is 
> over-engineered, I would say: Maybe.

I'm not at all against the presence of three devices. It's only a bad
idea to use the struct device_d * as a reference between functions. In
the MCI framework all functions take some device and then the
platform_data is derefenced to three different struct types. How do I
know which of the three devices is passed there? I have to look at the
calling function figure this out. We can simply let the compiler barf
when somebody passes a wrong pointer type when we do it like we always
did: Just pass a struct mci_host or whatever around.

Sascha

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