linux-kernel - Re: [PATCH 29/30] W1: Documentation/w1/masters/ds2490 update

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Message-Id: <20080717145252.ee6fcb19.randy.dunlap@oracle.com>
Date:	Thu, 17 Jul 2008 14:52:52 -0700
From:	Randy Dunlap <randy.dunlap@...cle.com>
To:	David Fries <david@...es.net>
Cc:	Evgeniy Polyakov <johnpol@....mipt.ru>,
	linux-kernel@...r.kernel.org,
	Andrew Morton <akpm@...ux-foundation.org>
Subject: Re: [PATCH 29/30] W1: Documentation/w1/masters/ds2490 update

On Mon, 14 Jul 2008 21:16:56 -0500 David Fries wrote:

> On Mon, Jul 14, 2008 at 01:40:02PM -0700, Randy Dunlap wrote:
> > > +- The number of USB bus transactions could be reduced if w1_reset_send
> > > +  was added to the API.  The name is just a suggestion.  It would take
> > > +  a write buffer and a read buffer (along with sizes) as arguments.
> > > +  It would add match rom and rom to the send buffer, reset the bus,
> >                   ~~~~~~~~~~~~~~~~~
> > Can you clarify above?
> 
> I re-wrote the paragraph.  In the one wire protocol a bus reset is
> followed by a one byte command, in this case match rom which tells all
> the devices on the bus to expect an 8byte rom (slave device id) and
> only the slave device that matches the rom is to respond to the
> following message.  I was assuming people reading it would be familiar
> with the one wire bus protocol.  Do you have any of the one wire
> hardware?

No. :(

> - The number of USB bus transactions could be reduced if w1_reset_send
>   was added to the API.  The name is just a suggestion.  It would take
>   a write buffer and a read buffer (along with sizes) as arguments.
>   The ds2490 block I/O command supports reset, write buffer, read
>   buffer, and strong pullup all in one command, instead of the current
>   1 reset bus, 2 write the match rom command and slave rom id, 3 block
>   write and read data.  The write buffer needs to have the match rom
>   command and slave rom id prepended to the front of the requested
>   write buffer, both of which are known to the driver.  
> 
> The next paragraph was removed, I decided that listing the commands
> giong from three to one was enough, I didn't need to count all the USB
> bus transactions.
> 
> I'll send the patch again in the next e-mail.

Thanks.

---
~Randy
Linux Plumbers Conference, 17-19 September 2008, Portland, Oregon USA
http://linuxplumbersconf.org/
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