[PATCH 3/9] gpio: Allow hogged gpios to be requested
From: Uwe Kleine-König <hidden>
Date: 2015-07-17 20:27:05
Also in:
linux-gpio
Hello, On Fri, Jul 17, 2015 at 11:32:44AM +0200, Markus Pargmann wrote:
quoted hunk ↗ jump to hunk
It can be useful to claim hogged gpios later, for example from userspace. This allows to set defaults for GPIOs using the hogging mechanism and override the setup later from userspace or a kernel driver. This patch adds a check for hogged gpios to allow requesting them. If the gpio is not hogged but marked as requested, it still fails with -EBUSY. Signed-off-by: Markus Pargmann <redacted> --- drivers/gpio/gpiolib.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-)diff --git a/drivers/gpio/gpiolib.c b/drivers/gpio/gpiolib.c index bf4bd1d120c3..9f402b159cbe 100644 --- a/drivers/gpio/gpiolib.c +++ b/drivers/gpio/gpiolib.c@@ -798,7 +798,8 @@ static int __gpiod_request(struct gpio_desc *desc, const char *label) * before IRQs are enabled, for non-sleeping (SOC) GPIOs. */ - if (test_and_set_bit(FLAG_REQUESTED, &desc->flags) == 0) { + if (test_and_set_bit(FLAG_REQUESTED, &desc->flags) == 0 || + test_and_clear_bit(FLAG_IS_HOGGED, &desc->flags) == 1) { desc_set_label(desc, label ? : "?"); status = 0;
I don't like this patch. IMHO hogging is a "use" of a GPIO that should prevent it being requested. While I think it's useful to be able to export some hogged pins I don't think this should be possible for all hogged pins unconditionally. And for gpios being used by drivers I'd expect they don't need to be hogged at all. I don't have a good idea how to solve that. Adding another property to a gpio that should be allowd to be exported can hardly count as hardware description and so doesn't belong in a device tree?! Please don't consider this objection as a reason for a NACK, only as starting point for a discussion. Apart from that: Does this result in hogged gpios being able to be requested by two additional drivers in parallel? Maybe the IS_HOGGED flag should be dropped when the gpio is requested? Best regards Uwe -- Pengutronix e.K. | Uwe Kleine-K?nig | Industrial Linux Solutions | http://www.pengutronix.de/ |