linux-kernel - Re: [PATCH/RFC 2.6.20-rc4 1/1] fbdev,mm: hecuba/E-Ink fbdev driver

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Date:	Fri, 12 Jan 2007 11:47:30 +1100
From:	Nick Piggin <nickpiggin@...oo.com.au>
To:	Jaya Kumar <jayakumar.lkml@...il.com>
CC:	Andrew Morton <akpm@...l.org>,
	linux-fbdev-devel@...ts.sourceforge.net,
	linux-kernel@...r.kernel.org, linux-mm@...ck.org
Subject: Re: [PATCH/RFC 2.6.20-rc4 1/1] fbdev,mm: hecuba/E-Ink fbdev driver

Jaya Kumar wrote:
> On 1/11/07, Andrew Morton <akpm@...l.org> wrote:
> 
>> That's all very interesting.
>>
>> Please don't dump a bunch of new implementation concepts like this on us
>> with no description of what it does, why it does it and why it does it in
>> this particular manner.
> 
> 
> Hi Andrew,
> 
> Actually, I didn't dump without description. :-) I had posted an RFC
> and an explanation of the design to the lists. Here's an archive link
> to that post. 
> http://marc.theaimsgroup.com/?l=linux-kernel&m=116583546411423&w=2
> I wasn't sure whether to include that description with the patch email
> because it was long.
> 
>> From that email:
> 
> ---
> This is there in order to hide the latency
> associated with updating the display (500ms to 800ms). The method used
> is to fake a framebuffer in memory. Then use pagefaults followed by delayed
> unmaping and only then do the actual framebuffer update. To explain this
> better, the usage scenario is like this:
> 
> - userspace app like Xfbdev mmaps framebuffer
> - driver handles and sets up nopage and page_mkwrite handlers
> - app tries to write to mmaped vaddress
> - get pagefault and reaches driver's nopage handler
> - driver's nopage handler finds and returns physical page ( no
>  actual framebuffer )
> - write so get page_mkwrite where we add this page to a list
> - also schedules a workqueue task to be run after a delay
> - app continues writing to that page with no additional cost
> - the workqueue task comes in and unmaps the pages on the list, then
>  completes the work associated with updating the framebuffer

Have you thought about implementing a traditional write-back cache using
the dirty bits, rather than unmapping the page?

-- 
SUSE Labs, Novell Inc.
Send instant messages to your online friends http://au.messenger.yahoo.com 
-
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/