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From:   Kent Gibson <warthog618@gmail.com>
To:     linux-kernel@vger.kernel.org, linux-gpio@vger.kernel.org,
        bgolaszewski@baylibre.com, linus.walleij@linaro.org
Cc:     Kent Gibson <warthog618@gmail.com>
Subject: [PATCH v2 08/18] gpiolib: cdev: support GPIOLINE_SET_CONFIG_IOCTL
Date:   Sat, 25 Jul 2020 12:19:45 +0800
Message-Id: <20200725041955.9985-9-warthog618@gmail.com>
In-Reply-To: <20200725041955.9985-1-warthog618@gmail.com>
References: <20200725041955.9985-1-warthog618@gmail.com>
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Sender: linux-kernel-owner@vger.kernel.org
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Add support for GPIOLINE_SET_CONFIG_IOCTL, the uAPI v2
line set config ioctl.

Signed-off-by: Kent Gibson <warthog618@gmail.com>
---
 drivers/gpio/gpiolib-cdev.c | 91 +++++++++++++++++++++++++++++++++++++
 1 file changed, 91 insertions(+)

diff --git a/drivers/gpio/gpiolib-cdev.c b/drivers/gpio/gpiolib-cdev.c
index 8caebb460557..9d944ca0ff59 100644
--- a/drivers/gpio/gpiolib-cdev.c
+++ b/drivers/gpio/gpiolib-cdev.c
@@ -16,6 +16,7 @@
 #include <linux/kernel.h>
 #include <linux/kfifo.h>
 #include <linux/module.h>
+#include <linux/mutex.h>
 #include <linux/pinctrl/consumer.h>
 #include <linux/poll.h>
 #include <linux/spinlock.h>
@@ -417,6 +418,8 @@ struct edge_detector {
  * @seqno: the sequence number for edge events generated on all lines in
  * this line request.  Note that this is not used when @num_descs is 1, as
  * the line_seqno is then the same and is cheaper to calculate.
+ * @config_mutex: mutex for serializing ioctl() calls to ensure consistency
+ * of configuration, partiuclarly multi-step accesses to desc flags.
  * @edets: an array of edge detectors, of size @num_descs
  * @descs: the GPIO descriptors held by this line request, with @num_descs
  * elements.
@@ -428,6 +431,7 @@ struct line {
 	wait_queue_head_t wait;
 	DECLARE_KFIFO_PTR(events, struct gpioline_event);
 	atomic_t seqno;
+	struct mutex config_mutex;
 	struct edge_detector *edets;
 	/* descs must be last so it can be dynamically sized */
 	struct gpio_desc *descs[];
@@ -709,6 +713,30 @@ static int gpioline_config_validate(struct gpioline_config *lc, int num_lines)
 	return 0;
 }
 
+static int gpioline_config_change_validate(struct line *line,
+					   struct gpioline_config *lc)
+{
+	int i;
+	u64 flags;
+	struct gpio_desc *desc;
+
+	for (i = 0; i < line->num_descs; i++) {
+		desc = line->descs[i];
+		flags = gpioline_config_flags(lc, i);
+		/* disallow edge detection changes */
+		if (line->edets[i].flags != (flags & GPIOLINE_EDGE_FLAGS))
+			return -EINVAL;
+
+		if (line->edets[i].flags) {
+			/* disallow polarity changes */
+			if (test_bit(FLAG_ACTIVE_LOW, &desc->flags) !=
+			    ((flags & GPIOLINE_FLAG_V2_ACTIVE_LOW) != 0))
+				return -EINVAL;
+		}
+	}
+	return 0;
+}
+
 static void gpioline_config_flags_to_desc_flags(u64 flags,
 						unsigned long *flagsp)
 {
@@ -757,6 +785,66 @@ static long line_get_values(struct line *line, void __user *ip)
 	return 0;
 }
 
+static long line_set_config_locked(struct line *line,
+				   struct gpioline_config *lc)
+{
+	struct gpio_desc *desc;
+	int i, ret;
+	u64 flags;
+
+	ret = gpioline_config_change_validate(line, lc);
+	if (ret)
+		return ret;
+
+	for (i = 0; i < line->num_descs; i++) {
+		desc = line->descs[i];
+		flags = gpioline_config_flags(lc, i);
+
+		gpioline_config_flags_to_desc_flags(flags, &desc->flags);
+		/*
+		 * Lines have to be requested explicitly for input
+		 * or output, else the line will be treated "as is".
+		 */
+		if (flags & GPIOLINE_FLAG_V2_OUTPUT) {
+			int val = gpioline_config_output_value(lc, i);
+
+			edge_detector_stop(&line->edets[i]);
+			ret = gpiod_direction_output(desc, val);
+			if (ret)
+				return ret;
+		} else if (flags & GPIOLINE_FLAG_V2_INPUT) {
+			ret = gpiod_direction_input(desc);
+			if (ret)
+				return ret;
+		}
+
+		blocking_notifier_call_chain(&desc->gdev->notifier,
+					     GPIOLINE_CHANGED_CONFIG, desc);
+	}
+	return 0;
+}
+
+static long line_set_config(struct line *line, void __user *ip)
+{
+	struct gpioline_config lc;
+	int ret;
+
+	if (copy_from_user(&lc, ip, sizeof(lc)))
+		return -EFAULT;
+
+	ret = gpioline_config_validate(&lc, line->num_descs);
+	if (ret)
+		return ret;
+
+	mutex_lock(&line->config_mutex);
+
+	ret = line_set_config_locked(line, &lc);
+
+	mutex_unlock(&line->config_mutex);
+
+	return ret;
+}
+
 static long line_ioctl(struct file *file, unsigned int cmd,
 		       unsigned long arg)
 {
@@ -765,6 +853,8 @@ static long line_ioctl(struct file *file, unsigned int cmd,
 
 	if (cmd == GPIOLINE_GET_VALUES_IOCTL)
 		return line_get_values(line, ip);
+	else if (cmd == GPIOLINE_SET_CONFIG_IOCTL)
+		return line_set_config(line, ip);
 
 	return -EINVAL;
 }
@@ -937,6 +1027,7 @@ static int line_create(struct gpio_device *gdev, void __user *ip)
 		}
 	}
 
+	mutex_init(&line->config_mutex);
 	init_waitqueue_head(&line->wait);
 	if (has_edge_detection) {
 		size = linereq.event_buffer_size;
-- 
2.27.0