[4.2.y-ckt stable] Patch "hwmon: (max1111) Return -ENODEV from max1111_read_channel if not instantiated" has been added to the 4.2.y-ckt tree

[Kamal Mostafa]

This is a note to let you know that I have just added a patch titled

    hwmon: (max1111) Return -ENODEV from max1111_read_channel if not instantiated

to the linux-4.2.y-queue branch of the 4.2.y-ckt extended stable tree 
which can be found at:

    http://kernel.ubuntu.com/git/ubuntu/linux.git/log/?h=linux-4.2.y-queue

This patch is scheduled to be released in version 4.2.8-ckt8.

If you, or anyone else, feels it should not be added to this tree, please 
reply to this email.

For more information about the 4.2.y-ckt tree, see
https://wiki.ubuntu.com/Kernel/Dev/ExtendedStable

Thanks.
-Kamal

---8<------------------------------------------------------------

>From 22f41dd3ff00976f5390d4593f5f2bf645d14da1 Mon Sep 17 00:00:00 2001
From: Guenter Roeck <linux at roeck-us.net>
Date: Sat, 26 Mar 2016 12:28:05 -0700
Subject: hwmon: (max1111) Return -ENODEV from max1111_read_channel if not
 instantiated

commit 3c2e2266a5bd2d1cef258e6e54dca1d99946379f upstream.

arm:pxa_defconfig can result in the following crash if the max1111 driver
is not instantiated.

Unhandled fault: page domain fault (0x01b) at 0x00000000
pgd = c0004000
[00000000] *pgd=00000000
Internal error: : 1b [#1] PREEMPT ARM
Modules linked in:
CPU: 0 PID: 300 Comm: kworker/0:1 Not tainted 4.5.0-01301-g1701f680407c #10
Hardware name: SHARP Akita
Workqueue: events sharpsl_charge_toggle
task: c390a000 ti: c391e000 task.ti: c391e000
PC is at max1111_read_channel+0x20/0x30
LR is at sharpsl_pm_pxa_read_max1111+0x2c/0x3c
pc : [<c03aaab0>]    lr : [<c0024b50>]    psr: 20000013
...
[<c03aaab0>] (max1111_read_channel) from [<c0024b50>]
					(sharpsl_pm_pxa_read_max1111+0x2c/0x3c)
[<c0024b50>] (sharpsl_pm_pxa_read_max1111) from [<c00262e0>]
					(spitzpm_read_devdata+0x5c/0xc4)
[<c00262e0>] (spitzpm_read_devdata) from [<c0024094>]
					(sharpsl_check_battery_temp+0x78/0x110)
[<c0024094>] (sharpsl_check_battery_temp) from [<c0024f9c>]
					(sharpsl_charge_toggle+0x48/0x110)
[<c0024f9c>] (sharpsl_charge_toggle) from [<c004429c>]
					(process_one_work+0x14c/0x48c)
[<c004429c>] (process_one_work) from [<c0044618>] (worker_thread+0x3c/0x5d4)
[<c0044618>] (worker_thread) from [<c004a238>] (kthread+0xd0/0xec)
[<c004a238>] (kthread) from [<c000a670>] (ret_from_fork+0x14/0x24)

This can occur because the SPI controller driver (SPI_PXA2XX) is built as
module and thus not necessarily loaded. While building SPI_PXA2XX into the
kernel would make the problem disappear, it appears prudent to ensure that
the driver is instantiated before accessing its data structures.

Cc: Arnd Bergmann <arnd at arndb.de>
Signed-off-by: Guenter Roeck <linux at roeck-us.net>
Signed-off-by: Kamal Mostafa <kamal at canonical.com>
---
 drivers/hwmon/max1111.c | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/drivers/hwmon/max1111.c b/drivers/hwmon/max1111.c
index f67d71e..159f50d 100644
--- a/drivers/hwmon/max1111.c
+++ b/drivers/hwmon/max1111.c
@@ -85,6 +85,9 @@ static struct max1111_data *the_max1111;

 int max1111_read_channel(int channel)
 {
+	if (!the_max1111 || !the_max1111->spi)
+		return -ENODEV;
+
 	return max1111_read(&the_max1111->spi->dev, channel);
 }
 EXPORT_SYMBOL(max1111_read_channel);
@@ -258,6 +261,9 @@ static int max1111_remove(struct spi_device *spi)
 {
 	struct max1111_data *data = spi_get_drvdata(spi);

+#ifdef CONFIG_SHARPSL_PM
+	the_max1111 = NULL;
+#endif
 	hwmon_device_unregister(data->hwmon_dev);
 	sysfs_remove_group(&spi->dev.kobj, &max1110_attr_group);
 	sysfs_remove_group(&spi->dev.kobj, &max1111_attr_group);
--
2.7.4