Messages in this thread | | | Date | Wed, 30 May 2012 12:10:58 +0800 | From | Dong Aisheng <> | Subject | Re: [PATCH v4 4/6] gpio: introduce lock mechanism for gpiochip_find |
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Hi Grant,
On Fri, May 25, 2012 at 06:25:00PM -0600, Grant Likely wrote: > On Fri, 25 May 2012 21:36:18 +0800, Dong Aisheng <b29396@freescale.com> wrote: > > From: Dong Aisheng <dong.aisheng@linaro.org> > > > > The module lock will be automatically claimed for gpiochip_find function > > in case the gpio module is removed during the using of gpiochip instance. > > Users are responsible to call gpiochip_put to release the lock after > > the using. > > > > Signed-off-by: Dong Aisheng <dong.aisheng@linaro.org> > ... > Also, it doesn't do anything to protect against the gpio_chip being > removed after the gpio number is resolved, which means the gpio number > may no longer be valid, or may no longer point to the same gpio chip. > It looks like the locking protection needs to be wider to be useful. > I understand the issue now. It's correct that we did not lock gpio_chip before calling gpio_request after the gpio number is resolved.
I thought about adding a new API called of_gpio_request to hide the lock to users like: int of_gpio_request(..) { spin_lock_irqsave(&gpio_lock, flags); ret = of_get_named_gpio(..); if (ret < 0) do_err.. ret = gpio_request(..)
spin_unlock_irqrestore(&gpio_lock, flags); return ret; } But it seems it does not work since the gpio_request may sleep and we may need a new sleepable lock rather using the exist gpio_lock.
In the same time, i'm also thinking about a question that do we really need to do this to protect gpio_chip being removed afer gpio number is resolved? My doubts is that gpio lib really does not block the gpiochip to be removed before calling gpio_request, so why we need to do that for dt? Maybe just let gpio_request to detect if gpio number is valid is already ok for dt.
what's your suggestion on it?
Regards Dong Aisheng
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