Re: PATCH: soc-camera: use flag for colour / bw camera instead of module parameter

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

On Tue, Jul 15, 2008 at 10:43:53PM +0200, Guennadi Liakhovetski wrote:
> On Tue, 15 Jul 2008, Sascha Hauer wrote:
> 
> > Use a flag in struct soc_camera_link for differentiation between
> > a black/white and a colour camera rather than a module parameter.
> > This allows for having colour and black/white cameras in the same
> > system.
> > Note that this one breaks the phytec pcm027 pxa board as it makes it
> > impossible to switch between cameras on the command line. I will send
> > an updated version of this patch once I know this patch is acceptable
> > this way.
> 
> Yes, we did discuss this on IRC and I did agree to use a platform-provided 
> parameter to specify camera properties like colour / monochrome, but now 
> as I see it, I think, it might not be a very good idea. Having it as a 
> parameter you can just reload the driver with a different parameter to 
> test your colour camera in b/w mode. With this change you would need a new 
> kernel.

I think it's a more common case to specify the correct camera on a
per-board basis than to test a colour camera in b/w mode. Only
developers want to do this and they know how to start a new kernel,
right? ;)
Another thing that came to my mind is that this particular camera has an
internal PLL for pixel clock generation. It can use the pxa pixel clock
directly or the one from the PLL. At the moment there is no way to
specify which clock to use, so we might even want to add a pointer to a
camera specific struct to soc_camera_link. This would be the right place
to put colour/bw flags aswell.

> What about an array of module parameters? Specifying flags on the 
> command line is too weird, so, maybe colo(u)r=0,2 where numbers are 
> camera-IDs? Or even 0:0 with bus-IDs. Yes, you would have to add optional 
> camera-ID to the link struct.

I don't like module parameters for specifying my hardware. It
reminds me of the ISA days where you had to specify iobase/irq this way.

Sascha

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