Re: [PATCH] of: provide of_platform_unpopulate()

From: NAVEEN KRISHNA CHATRADHI
Date: Sat Jul 20 2013 - 01:03:47 EST

Hello Sebastian,

------- Original Message -------
Sender : Sebastian Andrzej Siewior<bigeasy@xxxxxxxxxxxxx>
Date : Jul 19, 2013 23:44 (GMT+05:30)
Title : [PATCH] of: provide of_platform_unpopulate()

So I called of_platform_populate() on a device to get each child device
probed and on rmmod and I need to reverse its doing. After a quick grep
I did what others did as well and rmmod ended in:

| Unable to handle kernel NULL pointer dereference at virtual address 00000018
| PC is at release_resource+0x18/0x80
| Process rmmod (pid: 2005, stack limit = 0xedc30238)
| [<c003add0>] (release_resource+0x18/0x80) from [<c0300e08>] (platform_device_del+0x78/0xac)
| [<c0300e08>] (platform_device_del+0x78/0xac) from [<c0301358>] (platform_device_unregister+0xc/0x18)

The problem is that platform_device_del() "releases" each ressource in its
tree. This does not work on platform_devices created by OF becuase they
were never added via insert_resource(). As a consequence old->parent in
__release_resource() is NULL and we explode while accessing ->child.
So I either I do something completly wrong _or_ nobody here tested the
rmmod path of their driver.

This patch provides a common function to unregister / remove devices
which added to the system via of_platform_populate(). While this works
now on my test case I have not tested any of the driver I modify here so
feedback is greatly appreciated.
I've tested this on the exynos_adc driver under iio/adc/
and found a bug in the driver. When I fix the bug, your change happily rmmods the module.

Will send the patch separately.
Thanks for pointing out the bug for me.

Cc: Tony Lindgren <tony@xxxxxxxxxxx>
Cc: Doug Anderson <dianders@xxxxxxxxxxxx>
Cc: Vivek Gautam <gautam.vivek@xxxxxxxxxxx>
Cc: Naveen Krishna Chatradhi <ch.naveen@xxxxxxxxxxx>
Cc: Kukjin Kim <kgene.kim@xxxxxxxxxxx>
Cc: Kishon Vijay Abraham I <kishon@xxxxxx>
Cc: Roger Quadros <rogerq@xxxxxx>
Cc: George Cherian <george.cherian@xxxxxx>
Cc: Felipe Balbi <balbi@xxxxxx>
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@xxxxxxxxxxxxx>
---
drivers/bus/omap-ocp2scp.c | 13 ++-----------
drivers/iio/adc/exynos_adc.c | 15 ++-------------
drivers/mfd/omap-usb-host.c | 9 +--------
drivers/of/platform.c | 22 ++++++++++++++++++++++
drivers/usb/dwc3/dwc3-exynos.c | 11 +----------
drivers/usb/dwc3/dwc3-omap.c | 12 +-----------
include/linux/of_platform.h | 4 ++++
7 files changed, 33 insertions(+), 53 deletions(-)

diff --git a/drivers/bus/omap-ocp2scp.c b/drivers/bus/omap-ocp2scp.c
index 5511f98..510bb9e 100644
--- a/drivers/bus/omap-ocp2scp.c
+++ b/drivers/bus/omap-ocp2scp.c
@@ -23,15 +23,6 @@
#include <linux/of.h>
#include <linux/of_platform.h>

-static int ocp2scp_remove_devices(struct device *dev, void *c)
-{
- struct platform_device *pdev = to_platform_device(dev);
-
- platform_device_unregister(pdev);
-
- return 0;
-}
-
static int omap_ocp2scp_probe(struct platform_device *pdev)
{
int ret;
@@ -51,7 +42,7 @@ static int omap_ocp2scp_probe(struct platform_device *pdev)
return 0;

err0:
- device_for_each_child(&pdev->dev, NULL, ocp2scp_remove_devices);
+ of_platform_unpopulate(&pdev->dev);

return ret;
}
@@ -59,7 +50,7 @@ static int omap_ocp2scp_probe(struct platform_device *pdev)
static int omap_ocp2scp_remove(struct platform_device *pdev)
{
pm_runtime_disable(&pdev->dev);
- device_for_each_child(&pdev->dev, NULL, ocp2scp_remove_devices);
+ of_platform_unpopulate(&pdev->dev);

return 0;
}
diff --git a/drivers/iio/adc/exynos_adc.c b/drivers/iio/adc/exynos_adc.c
index 9809fc9..10248e1 100644
--- a/drivers/iio/adc/exynos_adc.c
+++ b/drivers/iio/adc/exynos_adc.c
@@ -216,15 +216,6 @@ static const struct iio_chan_spec exynos_adc_iio_channels[] = {
ADC_CHANNEL(9, "adc9"),
};

-static int exynos_adc_remove_devices(struct device *dev, void *c)
-{
- struct platform_device *pdev = to_platform_device(dev);
-
- platform_device_unregister(pdev);
-
- return 0;
-}
-
static void exynos_adc_hw_init(struct exynos_adc *info)
{
u32 con1, con2;
@@ -357,8 +348,7 @@ static int exynos_adc_probe(struct platform_device *pdev)
return 0;

err_of_populate:
- device_for_each_child(&pdev->dev, NULL,
- exynos_adc_remove_devices);
+ of_platform_unpopulate(&pdev->dev);
regulator_disable(info->vdd);
clk_disable_unprepare(info->clk);
err_iio_dev:
@@ -375,8 +365,7 @@ static int exynos_adc_remove(struct platform_device *pdev)
struct iio_dev *indio_dev = platform_get_drvdata(pdev);
struct exynos_adc *info = iio_priv(indio_dev);

- device_for_each_child(&pdev->dev, NULL,
- exynos_adc_remove_devices);
+ of_platform_unpopulate(&pdev->dev);
regulator_disable(info->vdd);
clk_disable_unprepare(info->clk);
writel(0, info->enable_reg);
diff --git a/drivers/mfd/omap-usb-host.c b/drivers/mfd/omap-usb-host.c
index 759fae3..bb26cea 100644
--- a/drivers/mfd/omap-usb-host.c
+++ b/drivers/mfd/omap-usb-host.c
@@ -832,13 +832,6 @@ static int usbhs_omap_probe(struct platform_device *pdev)
return ret;
}

-static int usbhs_omap_remove_child(struct device *dev, void *data)
-{
- dev_info(dev, "unregistering
");
- platform_device_unregister(to_platform_device(dev));
- return 0;
-}
-
/**
* usbhs_omap_remove - shutdown processing for UHH & TLL HCDs
* @pdev: USB Host Controller being removed
@@ -871,7 +864,7 @@ static int usbhs_omap_remove(struct platform_device *pdev)
pm_runtime_disable(&pdev->dev);

/* remove children */
- device_for_each_child(&pdev->dev, NULL, usbhs_omap_remove_child);
+ of_platform_unpopulate(&pdev->dev);
return 0;
}

diff --git a/drivers/of/platform.c b/drivers/of/platform.c
index e0a6514..9cbb0c3 100644
--- a/drivers/of/platform.c
+++ b/drivers/of/platform.c
@@ -473,4 +473,26 @@ int of_platform_populate(struct device_node *root,
return rc;
}
EXPORT_SYMBOL_GPL(of_platform_populate);
+
+static int of_remove_populated_child(struct device *dev, void *d)
+{
+ struct platform_device *pdev = to_platform_device(dev);
+
+ of_device_unregister(pdev);
+ return 0;
+}
+/**
+ * of_platform_unpopulate() - Remove populated devices.
+ * @parent: parent of the populated devices.
+ *
+ * The reverse of of_platform_populate() and can only be used a parent was
+ * specified while invoking the former.
+ */
+void of_platform_unpopulate(struct device *parent)
+{
+ if (WARN_ON(!parent))
+ return;
+ device_for_each_child(parent, NULL, of_remove_populated_child);
+}
+EXPORT_SYMBOL_GPL(of_platform_unpopulate);
#endif /* CONFIG_OF_ADDRESS */
diff --git a/drivers/usb/dwc3/dwc3-exynos.c b/drivers/usb/dwc3/dwc3-exynos.c
index 8ce9d7f..2bf5664 100644
--- a/drivers/usb/dwc3/dwc3-exynos.c
+++ b/drivers/usb/dwc3/dwc3-exynos.c
@@ -86,15 +86,6 @@ static int dwc3_exynos_register_phys(struct dwc3_exynos *exynos)
return ret;
}

-static int dwc3_exynos_remove_child(struct device *dev, void *unused)
-{
- struct platform_device *pdev = to_platform_device(dev);
-
- platform_device_unregister(pdev);
-
- return 0;
-}
-
static int dwc3_exynos_probe(struct platform_device *pdev)
{
struct dwc3_exynos *exynos;
@@ -164,7 +155,7 @@ static int dwc3_exynos_remove(struct platform_device *pdev)
{
struct dwc3_exynos *exynos = platform_get_drvdata(pdev);

- device_for_each_child(&pdev->dev, NULL, dwc3_exynos_remove_child);
+ of_platform_unpopulate(&pdev->dev);
platform_device_unregister(exynos->usb2_phy);
platform_device_unregister(exynos->usb3_phy);

diff --git a/drivers/usb/dwc3/dwc3-omap.c b/drivers/usb/dwc3/dwc3-omap.c
index 077f110..8688613 100644
--- a/drivers/usb/dwc3/dwc3-omap.c
+++ b/drivers/usb/dwc3/dwc3-omap.c
@@ -327,15 +327,6 @@ static irqreturn_t dwc3_omap_interrupt(int irq, void *_omap)
return IRQ_HANDLED;
}

-static int dwc3_omap_remove_core(struct device *dev, void *c)
-{
- struct platform_device *pdev = to_platform_device(dev);
-
- platform_device_unregister(pdev);
-
- return 0;
-}
-
static void dwc3_omap_enable_irqs(struct dwc3_omap *omap)
{
u32 reg;
@@ -529,8 +520,7 @@ static int dwc3_omap_remove(struct platform_device *pdev)
dwc3_omap_disable_irqs(omap);
pm_runtime_put_sync(&pdev->dev);
pm_runtime_disable(&pdev->dev);
- device_for_each_child(&pdev->dev, NULL, dwc3_omap_remove_core);
-
+ of_platform_unpopulate(&pdev->dev);
return 0;
}

diff --git a/include/linux/of_platform.h b/include/linux/of_platform.h
index 05cb4a9..e354f9c 100644
--- a/include/linux/of_platform.h
+++ b/include/linux/of_platform.h
@@ -72,6 +72,7 @@ extern int of_platform_populate(struct device_node *root,
const struct of_device_id *matches,
const struct of_dev_auxdata *lookup,
struct device *parent);
+extern void of_platform_unpopulate(struct device *parent);
#else
static inline int of_platform_populate(struct device_node *root,
const struct of_device_id *matches,
@@ -80,6 +81,9 @@ static inline int of_platform_populate(struct device_node *root,
{
return -ENODEV;
}
+static inline void of_platform_unpopulate(struct device *parent)
+{
+}
#endif

#endif /* _LINUX_OF_PLATFORM_H */
--
1.8.3.2

<p>&nbsp;</p><p>&nbsp;</p>Thanks & Best Regards,
Naveen Krishna Ch
SE @ Samsung-B.LABèº{.nÇ+‰·Ÿ®‰­†+%ŠËlzwm…éb?맲æìr¸›zX§»®w¥Š{ayºʇڙë,j­¢f£¢·hš‹àz¹®w¥¢¸ ¢·¦j:+v‰¨ŠwèjØm¶Ÿÿ¾«‘êçzZ+ƒùšŽŠÝ¢j"?ú!¶iO•æ¬z·švØ^¶m§ÿðà nÆŠàþY&—