linux-kernel - Re: [PATCH] spi: Add the flag indicate to registe new device as children of master or not.

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Date:	Fri, 21 Dec 2012 19:06:18 +0000
From:	Grant Likely <grant.likely@...retlab.ca>
To:	Jun Chen <jun.d.chen@...el.com>
Cc:	Mark Brown <broonie@...nsource.wolfsonmicro.com>,
	linux-kernel@...r.kernel.org, Bi Chao <chao.bi@...el.com>,
	spi-devel-general@...ts.sourceforge.net, jun.zhang@...el.com
Subject: Re: [PATCH] spi: Add the flag indicate to registe new device as children of master or not.

On Fri, 21 Dec 2012 12:39:52 -0500, Jun Chen <jun.d.chen@...el.com> wrote:
> On Wed, 2012-12-19 at 16:21 +0000, Grant Likely wrote:
> > On Wed, 19 Dec 2012 09:04:16 +0000, Mark Brown <broonie@...nsource.wolfsonmicro.com> wrote:
> > > On Wed, Dec 19, 2012 at 04:44:03AM -0500, Jun Chen wrote:
> > > 
> > > > This spi_alloc_device function will be called in the spi_new_device
> > > > function to alloc new device as the master. But other way, it is called
> > > > by the of_register_spi_devices function to register new device as the
> > > > children of the master. I will update changlog to add it. 
> > > 
> > > But why is this a bad thing?  You've said what's happening but not why
> > > it's a problem.
> > 
> > spi_devices should always be children of the spi_master. If that is not
> > the case then it is a bug to be fixed.
> > 
> 
> When many boards initializing, boards will call function
> spi_register_board_info to create bi->board_info,Then spi driver probe
> to call spi_register_master to register the driver and in the function
> spi_match_master_to_boardinfo To create new spi device, and this cases
> the spi_devices are not children of the spi_master.
> Many drivers do these steps. If all spi_devices must be children of the
> spi_master, Do spi core have plan to delete this way? 
> Or spi core can hold this way for many drivers. 

Let me make sure I understand what you're saying...

Right now, every spi_device object is registered as a child of an
spi_master object.

With this proposed patch, spi_devices registered via spi_register_board_info
will be siblings of the spi_master instead of children.

Do I understand correctly so far?

The problem is that I don't understand why this change is necessary.
spi_devices should always be children of an spi_master, not siblings.
What is the problem you're trying to solve with this change?

g.

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