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    Subject[PATCH 3.12 39/78] hwmon: (max1111) Return -ENODEV from max1111_read_channel if not instantiated
    Date
    From: Guenter Roeck <linux@roeck-us.net>

    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>]
    (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@arndb.de>
    Signed-off-by: Guenter Roeck <linux@roeck-us.net>
    Signed-off-by: Jiri Slaby <jslaby@suse.cz>
    ---
    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);
    }
    EXPORT_SYMBOL(max1111_read_channel);
    @@ -260,6 +263,9 @@ 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);
    --
    2.8.1
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