On Tue, Feb 11, 2014 at 3:55 PM, Josh Cartwright <joshc@xxxxxxxxxxxxxx> wrote:
> On Tue, Feb 11, 2014 at 03:30:33PM -0600, Rob Herring wrote:
>> On Tue, Feb 11, 2014 at 12:29 PM, Geert Uytterhoeven
>> <geert@xxxxxxxxxxxxxx> wrote:
>> > On Tue, Feb 11, 2014 at 7:08 PM, Josh Cartwright <joshc@xxxxxxxxxxxxxx> 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?
>> >
> [..]
>>
>> I believe this is the reason drivers have to call of_match_device:
>>
>> commit b1608d69cb804e414d0887140ba08a9398e4e638
>> Author: Grant Likely <grant.likely@xxxxxxxxxxxx>
>> 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@xxxxxxxxxxxx>
>
> Interesting, thanks for the history! I'm wondering if this same problem
> exists for the existing platform_device_id cached pointer as well.
>
> Okay, so maybe caching a pointer in the device isn't the best option,
> what if we considered extending the platform_driver callbacks to include
> a set of per-method (?) probe callbacks which do provide a handle to
> matched identifiers.
>
> In the case of a totally contrived platform_driver supporting ACPI, OF,
> and !OF configurations, it might look something like:
>
> static const struct of_device_id acme_of_table[] = {
> /* ... */
> { },
> };
> MODULE_DEVICE_TABLE(of, acme_of_table);
>
> static int acme_probe_of(struct platform_device *pdev,
> const struct of_device_id *id)
I don't think this is the right direction. You might want to look at
of_platform_driver in git history...
We still have something like this for macio_bus though.
Rob
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