On 02/06/2014 01:28 AM, Linus Walleij wrote:
On Wed, Feb 5, 2014 at 3:31 AM, Courtney Cavin
<courtney.cavin@xxxxxxxxxxxxxx> wrote:
>On Wed, Feb 05, 2014 at 12:08:35AM +0100, Christopher Heiny wrote:
>>On 01/23/2014 04:00 PM, Courtney Cavin wrote:
>> >Since all the configuration needed for an irq can be provided in other
>> >ways, remove all gpio->irq functionality. This cleans up the code quite
>> >a bit.
>>
>>In certain diagnostic modes, we need to be able to release the IRQ so
>>the GPIO can be monitored from userspace. This patch removes that
>>capability.
>
>Polling a GPIO from userspace is poor design regardless of the use-case, if
>you ask me. It certainly doesn't motivate the extra gpio<->IRQ code.
>
I think Courtney is right here, if you want this kind of stuff for debugging
it should be debug-add-on-patches, not part of the normal execution
path for the driver.
I'm OK with replacing the current polling implementation with an
add-on-patch, as long as the support for the debug-add-on-patches
doesn't get torn out of the driver because "hey, I don't see what this
is used for in the core driver code, so it must be unnecessary".
>>As mentioned in previous patch discussions, the polling functionality is
>>quite useful during new system integration, so we need to retain that.
>>If you have a proposal for where else it could be done, we'd certainly
>>entertain a patch that implements that.
>
>Do you actually have systems that have these hooked up to GPIOs without
>IRQ support?
>
>Regardless, if this is the case, implementing a GPIO polling IRQ chip
>should be possible, if extremely ugly.
OMG that would be quite horrible.
>Linus may have some comments in this area, though. Linus?
>
A driver may rely on polling but a driver may not rely on polling
done from userspace.
Fortunately, the driver doesn't rely on polling from user space.
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