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, 11 Jan 2013 14:57:54 +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 Mon, 24 Dec 2012 11:16:52 -0500, Jun Chen <jun.d.chen@...el.com> wrote:
> On Fri, 2012-12-21 at 19:06 +0000, Grant Likely wrote:
> > 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?
> > 
> When spi drivers try to use the core function(spi_register_master),it
> will trigger error,because they use the function
> spi_match_master_to_boardinfo  to create new spi device as the children
> of the master.
> In the old version of spi core, the new devices are registered as
> siblings of the spi_master. My spi driver based on the old version runs
> normal.
> 
> But after applying for this patch:
> {
>     spi: Fix device unregistration when unregistering the bus master
>     
>     Device are added as children of the bus master's parent device, but
>     spi_unregister_master() looks for devices to unregister in the bus
>     master's children. This results in the child devices not being
>     unregistered.
>     
>     Fix this by registering devices as direct children of the bus
> master.
> 
> 
> -	spi->dev.parent = dev;
> +	spi->dev.parent = &master->dev;
> }
> 
> Then my driver will be crash.
> Maybe I have mistake on this issue, thank for your more explanation and
> detail replay. 

Sounds like you've got a driver bug. Make sure it isn't trying to use
the spi_client parent pointer to find the device instance.

g.

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