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From: Kristoffer Ericson <>
To: Ben Dooks <>
Cc: Kristoffer Ericson <>,
	Linux Kernel <>
Subject: Re: Questions regarding mfd drivers
Date: Tue, 5 Feb 2008 12:21:27 +0100	[thread overview]
Message-ID: <> (raw)
In-Reply-To: <>

On Mon, 4 Feb 2008 23:01:55 +0000
Ben Dooks <> wrote:

> On Mon, Feb 04, 2008 at 12:37:14PM +0100, Kristoffer Ericson wrote:
> > Greetings,
> > 
> > Trying to wrap my head around sm501. From what I can tell an mfd driver is a "master" driver that takes control of all
> > memory and io areas. It then hands out areas of those to drivers. Anywhere near correct?
> Yes, it is the central management for these, but also ensures that any
> of the sub-drivers have properly locked access to the clocks, gpio and
> other shared resources.


> The mfd driver for the sm501 exports a number of functions for the
> sub drivers to use, you should be able to see what is exported easily
> by the fact they are exported with EXPORT_SYMBOL_GPL(). The header
> files should document basic functionality of this.

Will take a look at that.
> > I can see some benefit but still hard for me to motivate. What am I missing? What will the mfd be able to do, that I lack now?
> > 
> > The sm501 driver seems way more advanced than I will need for hd64461/hd64465 anyhow, but still need to understand sm501 completely before
> > attempting to write one on my own. Anyone know any documentation aside from example drivers?
> Are you trying to write your own SM501, or something else? It seems
> you are writing for something else.

Im trying to move the companion chip hd64461 to a more sensible location. Paul suggested building an mfd driver.
The hd64461 chipset supplies for example pcmcia and framebuffer support. Its not as advanced as the SM501.
> If the chip you are targetting has shared resources, such as clock
> gates, PLLs, or gpio that other drivers need to touch, then the best
> way to go is for an mfd driver to provide this functionality and have
> all the child drivers use the exported functionality.

Oki, sounds good. Thanks for info.

> -- 
> Ben (,
>   'a smiley only costs 4 bytes'

      reply	other threads:[~2008-02-05 11:21 UTC|newest]

Thread overview: 3+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2008-02-04 11:37 Kristoffer Ericson
2008-02-04 23:01 ` Ben Dooks
2008-02-05 11:21   ` Kristoffer Ericson [this message]

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