linux-kernel - [PATCH] gpiolib: notify user-space about line status changes after flags are set

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Date:   Sat,  9 May 2020 16:15:07 +0200
From:   Bartosz Golaszewski <brgl@...ev.pl>
To:     Kent Gibson <warthog618@...il.com>,
        Linus Walleij <linus.walleij@...aro.org>,
        Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
Cc:     linux-gpio@...r.kernel.org, linux-kernel@...r.kernel.org,
        Bartosz Golaszewski <bgolaszewski@...libre.com>
Subject: [PATCH] gpiolib: notify user-space about line status changes after flags are set

From: Bartosz Golaszewski <bgolaszewski@...libre.com>

Currently we emit the REQUESTED line state event after the line is
requested but before the flags are configured. This is obviously wrong
as we want to pass the updated lineinfo to user-space together with the
event.

Since the flags can be configured in different ways depending on how the
line is being requested - we need to call the notifier chain in different
places separately.

Fixes: 51c1064e82e7 ("gpiolib: add new ioctl() for monitoring changes in line info")
Signed-off-by: Bartosz Golaszewski <bgolaszewski@...libre.com>
---
This comes late in the release cycle but I only recently got down to
writing libgpiod support for this new ioctl(). When writing test cases
I noticed this doesn't really work as expected. This patch fixes the
issue I identified this week. There may be more coming the following
week though...

 drivers/gpio/gpiolib.c | 15 +++++++++++++--
 1 file changed, 13 insertions(+), 2 deletions(-)

diff --git a/drivers/gpio/gpiolib.c b/drivers/gpio/gpiolib.c
index 40f2d7f69be2..550751a6e51c 100644
--- a/drivers/gpio/gpiolib.c
+++ b/drivers/gpio/gpiolib.c
@@ -729,6 +729,10 @@ static int linehandle_create(struct gpio_device *gdev, void __user *ip)
 			if (ret)
 				goto out_free_descs;
 		}
+
+		atomic_notifier_call_chain(&desc->gdev->notifier,
+					   GPIOLINE_CHANGED_REQUESTED, desc);
+
 		dev_dbg(&gdev->dev, "registered chardev handle for line %d\n",
 			offset);
 	}
@@ -1083,6 +1087,9 @@ static int lineevent_create(struct gpio_device *gdev, void __user *ip)
 	if (ret)
 		goto out_free_desc;
 
+	atomic_notifier_call_chain(&desc->gdev->notifier,
+				   GPIOLINE_CHANGED_REQUESTED, desc);
+
 	le->irq = gpiod_to_irq(desc);
 	if (le->irq <= 0) {
 		ret = -ENODEV;
@@ -2975,8 +2982,6 @@ static int gpiod_request_commit(struct gpio_desc *desc, const char *label)
 	}
 done:
 	spin_unlock_irqrestore(&gpio_lock, flags);
-	atomic_notifier_call_chain(&desc->gdev->notifier,
-				   GPIOLINE_CHANGED_REQUESTED, desc);
 	return ret;
 }
 
@@ -4938,6 +4943,9 @@ struct gpio_desc *__must_check gpiod_get_index(struct device *dev,
 		return ERR_PTR(ret);
 	}
 
+	atomic_notifier_call_chain(&desc->gdev->notifier,
+				   GPIOLINE_CHANGED_REQUESTED, desc);
+
 	return desc;
 }
 EXPORT_SYMBOL_GPL(gpiod_get_index);
@@ -5003,6 +5011,9 @@ struct gpio_desc *fwnode_get_named_gpiod(struct fwnode_handle *fwnode,
 		return ERR_PTR(ret);
 	}
 
+	atomic_notifier_call_chain(&desc->gdev->notifier,
+				   GPIOLINE_CHANGED_REQUESTED, desc);
+
 	return desc;
 }
 EXPORT_SYMBOL_GPL(fwnode_get_named_gpiod);
-- 
2.25.0