Re: [PATCH] cyber2000fb: New framebuffer_alloc API and class_dev changes

[Russell King <rmk@arm.linux.org.uk>]

On Wed, Sep 17, 2003 at 08:37:29PM +0100, James Simmons wrote:
> 
> > - fbmem.c is responsible for managing the lifetime of the fb_info structure,
> >   and the lifetime of the driver-private data is equal to the lifetime
> >   of the fb_info structure.
> 
> This is not always the case. For dual headed graphics cards you can have 
> two struct fb_info and one driver-private data. If the fbdev driver
> releases one framebuffer you still have one framebuffer left that is using 
> the driver-private data.

If this is not true, then how can anyone even be thinking about applying
the sysfs / driver model to the framebuffer drivers.

Unless this sort of data lifetime rules are clearly and unabiguously
defined, there is no way that a sysfs / driver model "port" will ever
come anywhere near being stable.

You can't get around these problems with module usage counting - module
usage refcounting is solely about code lifetimes.  This is all about data
lifetimes - when is the data created, when can it be safely destroyed,
etc.

-- 
Russell King (rmk@arm.linux.org.uk)	http://www.arm.linux.org.uk/personal/
Linux kernel maintainer of:
  2.6 ARM Linux   - http://www.arm.linux.org.uk/
  2.6 PCMCIA      - http://pcmcia.arm.linux.org.uk/
  2.6 Serial core


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