# Re: \[PATCH 2.6.20 1/1\] fbdev, mm: hecuba/E-Ink fbdev driver

- From: Antonino A. Daplas \<adaplas@gmail.com\>
- Date: 2007-02-21 23:40:55 
- List: linux-fbdev
- Page: https://ratatoskr.run/linux-fbdev/2007/02/924040
- Thread: https://ratatoskr.run/linux-mm/2007/02/922264/t.md

```text
On Mon, 2007-02-19 at 23:13 -0500, Jaya Kumar wrote: 
> On 2/18/07, Paul Mundt [ref] wrote:
> > Given that, this would have to be something that's dealt with at the
> > subsystem level rather than in individual drivers, hence the desire to
> > see something like this more generically visible.
> >
> 
> Hi Peter, Paul, fbdev folk,
> 
> Ok. Here's what I'm thinking for abstracting this:
> 
> fbdev drivers would setup fb_mmap with their own_mmap as usual. In
> own_mmap, they would do what they normally do and setup a vm_ops. They
> are free to have their own nopage handler but would set the
> page_mkwrite handler to be fbdev_deferred_io_mkwrite().
> fbdev_deferred_io_mkwrite would build up the list of touched pages and
> pass it to a delayed workqueue which would then mkclean on each page

Yes, this functionality is sorely needed by more than a few driver
writers.

> and then pass a copy of that page list down to a driver's callback
> function. The fbdev driver's callback function can then do the actual
> IO to the framebuffer or coalesce DMA based on the provided page list.
> I would like to add something like the following to struct fb_info:
> 
> #ifdef CONFIG_FB_DEFERRED_IO
> struct fb_deferred_io *defio;
> #endif
> 
> to store the mutex (to protect the page list), the touched page list,
> and the driver's callback function.
> 
> I hope this sounds sufficiently generic to meet everyone's (the two of
> us? :) needs.

There's definitely more than two :-).  For the past several years,
various people have been asking for this functionality.  So yes,
implementing this in a generic manner will be a big help.

Tony


-------------------------------------------------------------------------
Take Surveys. Earn Cash. Influence the Future of IT
Join SourceForge.net's Techsay panel and you'll get the chance to share your
opinions on IT & business topics through brief surveys-and earn cash
http://www.techsay.com/default.php?page=join.php&p=sourceforge&CID=DEVDEV
```