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SubjectRe: [PATCH v2] HID: i2c-hid: add mutex protecting open/close race
On Wed, 12 Dec 2012, Benjamin Tissoires wrote:

> We should not enter close function while someone else is in open.
> This mutex prevents this race.
>
> There is also no need to override the ret value with -EIO in case of
> a failure of i2c_hid_set_power.
>
> Signed-off-by: Benjamin Tissoires <benjamin.tissoires@gmail.com>
> Reviewed-by: Jean Delvare <khali@linux-fr.org>
> ---
>
> Changes in v2:
> * add mutex.h

Applied, thanks.

>
> Cheers,
> Benjamin
>
> drivers/hid/i2c-hid/i2c-hid.c | 14 +++++++++++---
> 1 file changed, 11 insertions(+), 3 deletions(-)
>
> diff --git a/drivers/hid/i2c-hid/i2c-hid.c b/drivers/hid/i2c-hid/i2c-hid.c
> index 6e1774c..9ef22244 100644
> --- a/drivers/hid/i2c-hid/i2c-hid.c
> +++ b/drivers/hid/i2c-hid/i2c-hid.c
> @@ -33,6 +33,7 @@
> #include <linux/jiffies.h>
> #include <linux/kernel.h>
> #include <linux/hid.h>
> +#include <linux/mutex.h>
>
> #include <linux/i2c/i2c-hid.h>
>
> @@ -117,6 +118,8 @@ static const struct i2c_hid_cmd hid_set_power_cmd = { I2C_HID_CMD(0x08) };
> * static const struct i2c_hid_cmd hid_set_protocol_cmd = { I2C_HID_CMD(0x07) };
> */
>
> +static DEFINE_MUTEX(i2c_hid_open_mut);
> +
> /* The main device structure */
> struct i2c_hid {
> struct i2c_client *client; /* i2c client */
> @@ -641,17 +644,20 @@ static int i2c_hid_open(struct hid_device *hid)
> {
> struct i2c_client *client = hid->driver_data;
> struct i2c_hid *ihid = i2c_get_clientdata(client);
> - int ret;
> + int ret = 0;
>
> + mutex_lock(&i2c_hid_open_mut);
> if (!hid->open++) {
> ret = i2c_hid_set_power(client, I2C_HID_PWR_ON);
> if (ret) {
> hid->open--;
> - return -EIO;
> + goto done;
> }
> set_bit(I2C_HID_STARTED, &ihid->flags);
> }
> - return 0;
> +done:
> + mutex_unlock(&i2c_hid_open_mut);
> + return ret;
> }
>
> static void i2c_hid_close(struct hid_device *hid)
> @@ -663,12 +669,14 @@ static void i2c_hid_close(struct hid_device *hid)
> * data acquistion due to a resumption we no longer
> * care about
> */
> + mutex_lock(&i2c_hid_open_mut);
> if (!--hid->open) {
> clear_bit(I2C_HID_STARTED, &ihid->flags);
>
> /* Save some power */
> i2c_hid_set_power(client, I2C_HID_PWR_SLEEP);
> }
> + mutex_unlock(&i2c_hid_open_mut);
> }
>
> static int i2c_hid_power(struct hid_device *hid, int lvl)
> --
> 1.8.0.2
>

--
Jiri Kosina
SUSE Labs


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