Re: [PATCH 2.6.9-rc1-mm1] Disable colour conversion in the CPiA Video Camera driver

[Gerd Knorr <kraxel@bytesex.org>]

> Given that colour conversion is not allowed in kernel space, this patch
> disables it in the CPiA driver. The routines implementing the conversions
> can be removed at all by the maintainers of the driver; however, this
> patch is a good starting point and makes someone happy.

Yes, colorspace conversion shouldn't be done by the kernel but by the
applications.  I don't like the idea to just disable them through:

First: there should be a reasonable warning time for the current users.
Some printk message telling them they are using a depricated feature.
Maybe even a insmod option to enable/disable it, with the default being
software conversion disabled.

Second: IMHO it would be a very good idea to port the driver to the v4l2
API before ripping the in-kernel colorspace conversion support.  v4l2
provides a sane API to get a list of supported color formats, whereas
with v4l1 it is dirty trial-and-error + guesswork for the applications.

While thinking about it: due to the v4l1 trial-and-error mess a printk
likely generates alot of false positives, so a insmod option
(+rate-limited printk) is likely the better way to figure how much
userspace software breaks.  Maybe it isn't that much as other drivers
don't offer in-kernel conversion in the first place, so apps already
have to deal with that ...

  Gerd

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