linux-kernel - [patch 2.6.26-rc6-mm] gpio: updates to sysfs support

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Message-Id: <200806292050.45405.david-b@pacbell.net>
Date:	Sun, 29 Jun 2008 20:50:45 -0700
From:	David Brownell <david-b@...bell.net>
To:	Andrew Morton <akpm@...ux-foundation.org>
Cc:	lkml <linux-kernel@...r.kernel.org>
Subject: [patch 2.6.26-rc6-mm] gpio: updates to sysfs support

Update and bugfix the patch adding sysfs GPIO support:

  * Bugfix:  the test initializing the IS_OUT flag for output-only
    GPIOs had the sense inverted.

  * Update:  when gpio_chip.dev is provided, list it in the debugfs
    dump.  Device nodes are unique; the "label" isn't.

The bug of course caused output-only GPIOs to misbehave, but it also
made just-exported (or generally:  only-requested) GPIOs always appear
to be outputs in sysfs and debugfs.  That's wrong more often than it's
right, although it gets corrected when the direction is assigned.

Signed-off-by: David Brownell <dbrownell@...rs.sourceforge.net>
---
 drivers/gpio/gpiolib.c |   28 +++++++++++++++++++++++-----
 1 files changed, 23 insertions(+), 5 deletions(-)

--- a/drivers/gpio/gpiolib.c	2008-06-17 23:15:17.000000000 -0700
+++ b/drivers/gpio/gpiolib.c	2008-06-18 09:48:32.000000000 -0700
@@ -685,7 +685,14 @@ int gpiochip_add(struct gpio_chip *chip)
 	if (status == 0) {
 		for (id = base; id < base + chip->ngpio; id++) {
 			gpio_desc[id].chip = chip;
-			gpio_desc[id].flags = chip->direction_input
+
+			/* REVISIT:  most hardware initializes GPIOs as
+			 * inputs (often with pullups enabled) so power
+			 * usage is minimized.  Linux code should set the
+			 * gpio direction first thing; but until it does,
+			 * we may expose the wrong direction in sysfs.
+			 */
+			gpio_desc[id].flags = !chip->direction_input
 				? (1 << FLAG_IS_OUT)
 				: 0;
 		}
@@ -1108,17 +1115,28 @@ static int gpiolib_show(struct seq_file 
 	/* REVISIT this isn't locked against gpio_chip removal ... */
 
 	for (gpio = 0; gpio_is_valid(gpio); gpio++) {
+		struct device *dev;
+
 		if (chip == gpio_desc[gpio].chip)
 			continue;
 		chip = gpio_desc[gpio].chip;
 		if (!chip)
 			continue;
 
-		seq_printf(s, "%sGPIOs %d-%d, %s%s:\n",
+		seq_printf(s, "%sGPIOs %d-%d",
 				started ? "\n" : "",
-				chip->base, chip->base + chip->ngpio - 1,
-				chip->label ? : "generic",
-				chip->can_sleep ? ", can sleep" : "");
+				chip->base, chip->base + chip->ngpio - 1);
+		dev = chip->dev;
+		if (dev)
+			seq_printf(s, ", %s/%s",
+				dev->bus ? dev->bus->name : "no-bus",
+				dev->bus_id);
+		if (chip->label)
+			seq_printf(s, ", %s", chip->label);
+		if (chip->can_sleep)
+			seq_printf(s, ", can sleep");
+		seq_printf(s, ":\n");
+
 		started = 1;
 		if (chip->dbg_show)
 			chip->dbg_show(s, chip);
--
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