[PATCH 3.12 39/78] hwmon: (max1111) Return -ENODEV from max1111_read_channel if not instantiated

From: Jiri Slaby
Date: Fri Apr 22 2016 - 07:18:41 EST

From: Guenter Roeck <linux@xxxxxxxxxxxx>

3.12-stable review patch. If anyone has any objections, please let me know.


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>]
[<c0024b50>] (sharpsl_pm_pxa_read_max1111) from [<c00262e0>]
[<c00262e0>] (spitzpm_read_devdata) from [<c0024094>]
[<c0024094>] (sharpsl_check_battery_temp) from [<c0024f9c>]
[<c0024f9c>] (sharpsl_charge_toggle) from [<c004429c>]
[<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@xxxxxxxx>
Signed-off-by: Guenter Roeck <linux@xxxxxxxxxxxx>
Signed-off-by: Jiri Slaby <jslaby@xxxxxxx>
drivers/hwmon/max1111.c | 6 ++++++
1 file changed, 6 insertions(+)

diff --git a/drivers/hwmon/max1111.c b/drivers/hwmon/max1111.c
index eda077de8a9f..f787f04a0d1a 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);
@@ -260,6 +263,9 @@ static int max1111_remove(struct spi_device *spi)
struct max1111_data *data = spi_get_drvdata(spi);

+ the_max1111 = NULL;
sysfs_remove_group(&spi->dev.kobj, &max1110_attr_group);
sysfs_remove_group(&spi->dev.kobj, &max1111_attr_group);