[RFC PATCH] Rework gpio cansleep (was Re: gpiolib and sleepinggpios)

--- On Wed, 6/23/10, Jon Povey <Jon.Povey@racelogic.co.uk> wrote:

Date: Wednesday, June 23, 2010, 9:46 PM
Ryan Mallon wrote:

quoted

If we strip my patch back to just introducing

gpio_request_cansleep,

quoted

which would be used in any driver where all of the

calls are

quoted

gpio_(set/get)_cansleep, and make gpio_request only

allow non-sleeping

quoted

gpios then incorrect use of gpios would be caught at

request time and

quoted

returned to the caller as an error.

It seems like a good idea to catch these at request time.
There is support in the API for this already
(gpio_cansleep), but driver writers are not steered towards
checking and thinking in these ways by the current API or

gpio_request_cansleep would be the same as current
gpio_request

I wonder if, by the time I catch up on this
ever-extending email thread

... someone else will have noted that
because gpio_request() can now poke the GPIO
chip, that call might actually need to sleep.
So there'd be a difference between the two
calls:? one would *NEED* to be called in a
sleepable thread context, vs. that just being
well advised (e.g. as part of board setup in
arch init code after tasking is working)...

So that couldn't work quite that way.