Hi Alex,
On Mon, 16 Aug 2010 09:31:17 +0800, Axel Lin wrote:
> We need to call hwmon_device_unregister() if an error is detected after
> sucessfully register hwmon device.
>
> Signed-off-by: Axel Lin <axel.lin@xxxxxxxxx>
> ---
> drivers/hwmon/ads7871.c | 4 +++-
> 1 files changed, 3 insertions(+), 1 deletions(-)
>
> diff --git a/drivers/hwmon/ads7871.c b/drivers/hwmon/ads7871.c
> index b300a20..303db92 100644
> --- a/drivers/hwmon/ads7871.c
> +++ b/drivers/hwmon/ads7871.c
> @@ -201,11 +201,13 @@ static int __devinit ads7871_probe(struct spi_device *spi)
> we need to make sure we really have a chip*/
> if (val != ret) {
> err = -ENODEV;
> - goto error_remove;
> + goto error_unregister;
> }
>
> return 0;
>
> +error_unregister:
> + hwmon_device_unregister(pdata->hwmon_dev);
> error_remove:
> sysfs_remove_group(&spi->dev.kobj, &ads7871_group);
> error_free:
The bug is real, but I don't think the fix is correct. You should never
have to unregister the hwmon device in the error path, because you
should ensure the hardware is there and working _before_ you register
the hwmon device.
User-space could watch for hwmon devices being added or removed, and
you don't want to trigger such events for a device which isn't going to
work.
So I would suggest reworking the order in which things are done,
leaving hwmon_device_register() at the end of the function. This won't
only fix the error path, this will also close a race window, as for the
moment, the device is exposed to user-space _before_ it it properly
initialized, which is wrong.
Please send an updated patch and I'll be happy to apply it.
--
Jean Delvare
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