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Re: Default Kconfig state for hw_random drivers
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Olof Johansson
Apr 26, 2012, 10:17:35 AM4/26/12
to Mark Brown, Herbert Xu, Matt Mackall, linux-...@vger.kernel.org, Arnd Bergmann, Nicolas Ferre
On Thu, Apr 26, 2012 at 4:42 AM, Mark Brown
<bro...@opensource.wolfsonmicro.com> wrote:
> An Atmel hw_random driver just appeared in -next. Since it's just a
> regular platform device it has no dependencies on any particular
> platform so following the behaviour of other hw_random drivers it's set
> to default enabled if hw_random is enabled, even on non-Atmel platforms.
>
> This doesn't feel like the right thing to do - it'd mean that most of
> the embedded RNGs would end up getting enabled by default which probably
> isn't what we want.
Indeed, thanks for catching this. The driver isn't new but it had a
previous dependency on just one AT91 chip family.
Looking at other options in the same Kconfig, it would be appropriate
to make it depend on ARCH_AT91 instead.
Nicolas?
-Olof
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<bro...@opensource.wolfsonmicro.com> wrote:
> An Atmel hw_random driver just appeared in -next. Since it's just a
> regular platform device it has no dependencies on any particular
> platform so following the behaviour of other hw_random drivers it's set
> to default enabled if hw_random is enabled, even on non-Atmel platforms.
>
> This doesn't feel like the right thing to do - it'd mean that most of
> the embedded RNGs would end up getting enabled by default which probably
> isn't what we want.
Indeed, thanks for catching this. The driver isn't new but it had a
previous dependency on just one AT91 chip family.
Looking at other options in the same Kconfig, it would be appropriate
to make it depend on ARCH_AT91 instead.
Nicolas?
-Olof
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the body of a message to majo...@vger.kernel.org
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/
Nicolas Ferre
Apr 27, 2012, 8:31:57 AM4/27/12
to Olof Johansson, Mark Brown, Arnd Bergmann, ba...@ti.com, Herbert Xu, Matt Mackall, linux-...@vger.kernel.org
On 04/26/2012 04:17 PM, Olof Johansson :
I had the same kind of discussion with Felipe and Arnd in this thread:
http://thread.gmane.org/gmane.linux.ports.arm.kernel/122248/focus=122304
The conclusion came out after Arnd's strong arguments:
http://article.gmane.org/gmane.linux.ports.arm.kernel/122962
Maybe adding a "default" directive can be an valid option?
Best regards,
--
Nicolas Ferre
> On Thu, Apr 26, 2012 at 4:42 AM, Mark Brown
> <bro...@opensource.wolfsonmicro.com> wrote:
>> An Atmel hw_random driver just appeared in -next. Since it's just a
>> regular platform device it has no dependencies on any particular
>> platform so following the behaviour of other hw_random drivers it's set
>> to default enabled if hw_random is enabled, even on non-Atmel platforms.
>>
>> This doesn't feel like the right thing to do - it'd mean that most of
>> the embedded RNGs would end up getting enabled by default which probably
>> isn't what we want.
>
> Indeed, thanks for catching this. The driver isn't new but it had a
> previous dependency on just one AT91 chip family.
>
> Looking at other options in the same Kconfig, it would be appropriate
> to make it depend on ARCH_AT91 instead.
>
> Nicolas?
Hi,
> <bro...@opensource.wolfsonmicro.com> wrote:
>> An Atmel hw_random driver just appeared in -next. Since it's just a
>> regular platform device it has no dependencies on any particular
>> platform so following the behaviour of other hw_random drivers it's set
>> to default enabled if hw_random is enabled, even on non-Atmel platforms.
>>
>> This doesn't feel like the right thing to do - it'd mean that most of
>> the embedded RNGs would end up getting enabled by default which probably
>> isn't what we want.
>
> Indeed, thanks for catching this. The driver isn't new but it had a
> previous dependency on just one AT91 chip family.
>
> Looking at other options in the same Kconfig, it would be appropriate
> to make it depend on ARCH_AT91 instead.
>
> Nicolas?
I had the same kind of discussion with Felipe and Arnd in this thread:
http://thread.gmane.org/gmane.linux.ports.arm.kernel/122248/focus=122304
The conclusion came out after Arnd's strong arguments:
http://article.gmane.org/gmane.linux.ports.arm.kernel/122962
Maybe adding a "default" directive can be an valid option?
Best regards,
--
Nicolas Ferre
Arnd Bergmann
Apr 27, 2012, 8:56:06 AM4/27/12
to Mark Brown, Nicolas Ferre, Olof Johansson, ba...@ti.com, Herbert Xu, Matt Mackall, linux-...@vger.kernel.org
On Friday 27 April 2012, Mark Brown wrote:
> There is one, that's the problem - the driver is defaulting to the same
> state as the main hw_random option (as is idiomatic for this subsystem).
> This means that if you've enabled any hw_random device this driver will
> be enabled by default. I would argue that this default directive only
> makes sense if there's an explicit dependency limiting the platforms it
> can build on. If it can build on any platform then omitting the default
> and just defaulting to N as is normal for drivers would be better.
How about making it default to (HW_RANDOM && ARCH_AT91) then?
Arnd
> There is one, that's the problem - the driver is defaulting to the same
> state as the main hw_random option (as is idiomatic for this subsystem).
> This means that if you've enabled any hw_random device this driver will
> be enabled by default. I would argue that this default directive only
> makes sense if there's an explicit dependency limiting the platforms it
> can build on. If it can build on any platform then omitting the default
> and just defaulting to N as is normal for drivers would be better.
How about making it default to (HW_RANDOM && ARCH_AT91) then?
Arnd
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