pinctrl: allow exlusive GPIO/mux pin allocation

Disallow simultaneous use of the the GPIO and peripheral mux
functions by setting a flag "strict" in struct pinctrl_desc.

The blackfin pinmux and gpio controller doesn't allow user to
set up a pin for both GPIO and peripheral function. So, add flag
strict in struct pinctrl_desc to check both gpio_owner and
mux_owner before approving the pin request.

v2-changes:
- if strict flag is set, check gpio_owner and mux_onwer in if and
  else clause

v3-changes:
- add kerneldoc for this struct
- augment Documentation/pinctrl.txt

Signed-off-by: Sonic Zhang <sonic.zhang@analog.com>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>

1 files changed, 13 insertions, 0 deletions

diff --git a/drivers/pinctrl/pinmux.c b/drivers/pinctrl/pinmux.c
index b874458dcb88..2546fa783464 100644
--- a/drivers/pinctrl/pinmux.c
+++ b/drivers/pinctrl/pinmux.c
@@ -107,6 +107,13 @@ static int pin_request(struct pinctrl_dev *pctldev,
 				desc->name, desc->gpio_owner, owner);
 			goto out;
 		}
+		if (pctldev->desc->strict && desc->mux_usecount &&
+		    strcmp(desc->mux_owner, owner)) {
+			dev_err(pctldev->dev,
+				"pin %s already requested by %s; cannot claim for %s\n",
+				desc->name, desc->mux_owner, owner);
+			goto out;
+		}
 
 		desc->gpio_owner = owner;
 	} else {
@@ -116,6 +123,12 @@ static int pin_request(struct pinctrl_dev *pctldev,
 				desc->name, desc->mux_owner, owner);
 			goto out;
 		}
+		if (pctldev->desc->strict && desc->gpio_owner) {
+			dev_err(pctldev->dev,
+				"pin %s already requested by %s; cannot claim for %s\n",
+				desc->name, desc->gpio_owner, owner);
+			goto out;
+		}
 
 		desc->mux_usecount++;
 		if (desc->mux_usecount > 1)