On Sun, Jul 19, 2015 at 04:01:42PM +0200, Markus Pargmann wrote:

Hi Uwe,

On Fri, Jul 17, 2015 at 10:27:02PM +0200, Uwe Kleine-K?nig wrote:

quoted

Hello,

On Fri, Jul 17, 2015 at 11:32:44AM +0200, Markus Pargmann wrote:

quoted

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.

I disagree with you here. The original patch stated in its description
that it was designed to initialize GPIOs. In my understanding this does
not necessarily mean that a hogged GPIO has to be blocked forever.

IIRC, this use case was discussed but was rejected by Linus when hogs
were added:

	https://lkml.kernel.org/r/CACRpkdZcNcPBYQM438CZJx1gYst9BFBSTj-3Qv2aPGF9pdWa5g at mail.gmail.com

Linus?

Johan