linux-kernel - Re: [PATCH] of: Turn of_match_node into a static inline when CONFIG

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Message-ID: <CAL_JsqKnsr-9nSjCGvroC0nDK36vQUnwMWj=cPjvUbRymmHFOQ@mail.gmail.com>
Date:	Tue, 11 Feb 2014 15:30:33 -0600
From:	Rob Herring <robherring2@...il.com>
To:	Geert Uytterhoeven <geert@...ux-m68k.org>
Cc:	Josh Cartwright <joshc@...eaurora.org>,
	Laurent Pinchart <laurent.pinchart@...asonboard.com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
	Grant Likely <grant.likely@...aro.org>,
	Rob Herring <robh+dt@...nel.org>
Subject: Re: [PATCH] of: Turn of_match_node into a static inline when
 CONFIG_OF isn't set

On Tue, Feb 11, 2014 at 12:29 PM, Geert Uytterhoeven
<geert@...ux-m68k.org> wrote:
> On Tue, Feb 11, 2014 at 7:08 PM, Josh Cartwright <joshc@...eaurora.org> wrote:
>> It sure would be convenient if platform_device had a 'const struct
>> of_device_id *of_id_entry' member similar to the existing struct
>> platform_device_id one, that was set up during platform device matching.
>> Most platform_driver users of of_match_node() would simply go away.
>
> Can't the entry be shared for both platform_device_id and of_device_id?
> Only one of them can be valid at the same time, right?
>
> Ideally, all xxx_device_id look like
>
>     struct xxx_device_id {
>             ... /* bus-specific ID information */
>             kernel_ulong_t driver_data;
>     };
>
> This may be formalized in some way, using a base class, but thay may
> require reordering the fields, like:
>
>     struct base_device_id {
>             kernel_ulong_t driver_data;
>             long id[0];
>     };
>

I believe this is the reason drivers have to call of_match_device:

commit b1608d69cb804e414d0887140ba08a9398e4e638
Author: Grant Likely <grant.likely@...retlab.ca>
Date:   Wed May 18 11:19:24 2011 -0600

    drivercore: revert addition of of_match to struct device

    Commit b826291c, "drivercore/dt: add a match table pointer to struct
    device" added an of_match pointer to struct device to cache the
    of_match_table entry discovered at driver match time.  This was unsafe
    because matching is not an atomic operation with probing a driver.  If
    two or more drivers are attempted to be matched to a driver at the
    same time, then the cached matching entry pointer could get
    overwritten.

    This patch reverts the of_match cache pointer and reworks all users to
    call of_match_device() directly instead.

    Signed-off-by: Grant Likely <grant.likely@...retlab.ca>

Rob
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