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SubjectRe: [PATCH] w1-gpio: add external pull-up enable callback
(cc Andrew Morton)

Andrew,

could you add this to your patch queue? It's been acked by Ville Syrjala
and Evgeniy Polyakov.

Thanks,
Daniel


From 6a99f9453d9b0ad2dd705c012014063977781bf3 Mon Sep 17 00:00:00 2001
From: Daniel Mack <daniel@caiaq.de>
Date: Tue, 5 May 2009 14:35:04 +0200
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@caiaq.de>
Acked-by: Ville Syrjala <syrjala@sci.fi>
Acked-by: Evgeniy Polyakov <johnpol@2ka.mipt.ru>
---
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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