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

Randy Dunlap
2008-07-17T22:02:14Z

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