linux-kernel - [PATCH] w1-gpio: add external pull-up enable callback

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Date:	Tue,  5 May 2009 14:43:33 +0200
From:	Daniel Mack <daniel@...aq.de>
To:	linux-kernel@...r.kernel.org
Cc:	Daniel Mack <daniel@...aq.de>, Ville Syrjala <syrjala@....fi>
Subject: [PATCH] w1-gpio: add external pull-up enable callback

On embedded devices, sleep mode conditions can be tricky to handle,
Especially when processors tend to pull-down the w1 bus during sleep.
Bus slaves (such as the ds2760) may interpret this as a reason for
power-down conditions and entirely switch off the device.

This patch adds a callback function pointer to let users switch on and
off the external pull-up resistor. This lets the outside world know
whether the processor is currently actively driving the bus or not.

When this callback is not provided, the code behaviour won't change.

Signed-off-by: Daniel Mack <daniel@...aq.de>
Cc: Ville Syrjala <syrjala@....fi>
---
 drivers/w1/masters/w1-gpio.c |   35 +++++++++++++++++++++++++++++++++++
 include/linux/w1-gpio.h      |    1 +
 2 files changed, 36 insertions(+), 0 deletions(-)

diff --git a/drivers/w1/masters/w1-gpio.c b/drivers/w1/masters/w1-gpio.c
index a411702..6f8866d 100644
--- a/drivers/w1/masters/w1-gpio.c
+++ b/drivers/w1/masters/w1-gpio.c
@@ -74,6 +74,9 @@ static int __init w1_gpio_probe(struct platform_device *pdev)
 	if (err)
 		goto free_gpio;
 
+	if (pdata->enable_external_pullup)
+		pdata->enable_external_pullup(1);
+
 	platform_set_drvdata(pdev, master);
 
 	return 0;
@@ -91,6 +94,9 @@ static int __exit w1_gpio_remove(struct platform_device *pdev)
 	struct w1_bus_master *master = platform_get_drvdata(pdev);
 	struct w1_gpio_platform_data *pdata = pdev->dev.platform_data;
 
+	if (pdata->enable_external_pullup)
+		pdata->enable_external_pullup(0);
+
 	w1_remove_master_device(master);
 	gpio_free(pdata->pin);
 	kfree(master);
@@ -98,12 +104,41 @@ static int __exit w1_gpio_remove(struct platform_device *pdev)
 	return 0;
 }
 
+#ifdef CONFIG_PM
+
+static int w1_gpio_suspend(struct platform_device *pdev, pm_message_t state)
+{
+	struct w1_gpio_platform_data *pdata = pdev->dev.platform_data;
+
+	if (pdata->enable_external_pullup)
+		pdata->enable_external_pullup(0);
+
+	return 0;
+}
+
+static int w1_gpio_resume(struct platform_device *pdev)
+{
+	struct w1_gpio_platform_data *pdata = pdev->dev.platform_data;
+
+	if (pdata->enable_external_pullup)
+		pdata->enable_external_pullup(1);
+
+	return 0;
+}
+
+#else
+#define w1_gpio_suspend	NULL
+#define w1_gpio_resume	NULL
+#endif
+
 static struct platform_driver w1_gpio_driver = {
 	.driver = {
 		.name	= "w1-gpio",
 		.owner	= THIS_MODULE,
 	},
 	.remove	= __exit_p(w1_gpio_remove),
+	.suspend = w1_gpio_suspend,
+	.resume = w1_gpio_resume,
 };
 
 static int __init w1_gpio_init(void)
diff --git a/include/linux/w1-gpio.h b/include/linux/w1-gpio.h
index 9797fec..3adeff8 100644
--- a/include/linux/w1-gpio.h
+++ b/include/linux/w1-gpio.h
@@ -18,6 +18,7 @@
 struct w1_gpio_platform_data {
 	unsigned int pin;
 	unsigned int is_open_drain:1;
+	void (*enable_external_pullup)(int enable);
 };
 
 #endif /* _LINUX_W1_GPIO_H */
-- 
1.6.2.1

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