linux-kernel - Re: [PATCH] I2C: Make I2C core able to be module when I2C

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Message-ID: <20140813070759.GB1657@lahna.fi.intel.com>
Date:	Wed, 13 Aug 2014 10:07:59 +0300
From:	Mika Westerberg <mika.westerberg@...ux.intel.com>
To:	Lan Tianyu <tianyu.lan@...el.com>
Cc:	Wolfram Sang <wsa@...-dreams.de>, torvalds@...ux-foundation.org,
	linux-i2c@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] I2C: Make I2C core able to be module when I2C_ACPI is
 selected.

On Wed, Aug 13, 2014 at 10:50:32AM +0800, Lan Tianyu wrote:
> On 2014年08月13日 10:03, Wolfram Sang wrote:
> > On Tue, Aug 12, 2014 at 12:53:21PM +0300, Mika Westerberg wrote:
> >> On Mon, Aug 11, 2014 at 03:00:55PM +0800, Lan Tianyu wrote:
> >>> Commit da3c6647(I2C/ACPI: Clean up I2C ACPI code and Add CONFIG_I2C_ACPI
> >>> config) adds a new kernel config I2C_ACPI and make I2C core built in
> >>> when the config is selected. This is wrong because distributions
> >>> etc generally compile I2C as a module and the commit broken that.
> >>> This patch is to make I2C core able to be a module when I2C_ACPI is
> >>> selected. Original issue the commit da3c6647 tried to avoid will
> >>> be fixed in ACPICA and it's rarely triggered during unloading module. 
> >>>
> >>> Signed-off-by: Lan Tianyu <tianyu.lan@...el.com>
> >>
> >> I wonder if we can do
> >>
> >> 	depends on I2C=y
> >>
> >> here? If I understand it right, then we only build the ACPI_I2C if I2C
> >> is compiled into the kernel. That way the problem da3c6647 tried to
> >> solve doens't re-appear.
> >>
> >> We can later on relax this once ACPICA has been fixed. Thoughts?
> > 
> > I had the same idea yet my travel to Chicago interrupted thinking about
> > it further. Once I get rid of my jetlag, I'll have a closer look. Unless
> > you already came up with the perfect solution until then, of course ;)
> >
> 
> Hi Mika & Wolfram:
> 	I have one concern about "depends on I2C=y". If distribution config
> file selects I2C core as a module, the original code can enumerate I2C
> slave devices from ACPI table. But now I2C_ACPI depends on I2C core
> built in, the I2C module can't enumerate devices from ACPI table. This
> maybe a regression for distribution?

True, but only the I2C OpRegion parts needs to have I2C=y. Does it make
sense to name ACPI_I2C to ACPI_I2C_OPREGION (or something like that)
and only enable it when I2C=y? Then we would have ACPI I2C enumeration
still in place.
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