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SubjectRe: Platform device id
Hi Jean,

On 9/7/07, Jean Delvare <khali@linux-fr.org> wrote:
> Hi Greg, all,
>
> While platform_device.id is a u32, platform_device_add() handles "-1" as
> a special id value. This has potential for confusion and bugs. One such
> bug was reported to me by David Brownell:
>
> http://lists.lm-sensors.org/pipermail/i2c/2007-September/001787.html
>
> And since then I've found two other drivers affected (uartlite and
> i2c-pxa).
>
> Could we at least make platform_device.id an int so as to clear up the
> confusion? I doubt that the id will ever be a large number anyway.
>
> To go one step further, I am questioning the real value of this naming
> exception for these "unique" platform devices. On top of the bugs I
> mentioned above, it has potential for compatibility breakage: adding a
> second device of the same type will rename the first one from "foo" to
> "foo.0". It also requires specific checks in many individual platform
> drivers. All this, as I understand it, for a purely aesthetic reason. I
> don't think this is worth it. Would there be any objection to simply
> getting rid of this exception and having all platform devices named
> "foo.%d"?
>

If a device has a <name>.<instance> scheme this implies possibility of
having several instances of said device in a box. There are a few of
platform devices that can only have one instance - for example i8042
keyboard controller (the -1 special handling came from me because
i80420 name was very confusing - there wasn't a dot separator in the
name back then). Drivers that allow multiple devices should not
attempt to use -1 for the very first instance - this should eliminate
potential for error and special handling that you are talking about.

--
Dmitry
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