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SubjectRe: [PATCH] i8k: Fix temperature bug handling in i8k_get_temp()
On 11/18/2014 06:56 AM, Pali Rohár wrote:
> Static array prev[] was incorrectly initialized. It should be initialized to
> some "invalid" temperature value (above I8K_MAX_TEMP).
>
> Next, function should store "invalid" value to prev[] (above I8K_MAX_TEMP),
> not valid (= I8K_MAX_TEMP) because whole temperature bug handling will not
> work.
>
> And last part, to not break existing detection of temperature sensors, register
> them also if i8k report too high temperature (above I8K_MAX_TEMP). This is
> needed because some sensors are sometimes turned off (e.g sensor on GPU which
> can be turned off/on) and in this case SMM report too high value.
>
> To prevent reporting "invalid" values to userspace, return -EINVAL. In this case
> sensors which are currently turned off (e.g optimus/powerexpress/enduro gpu)
> are reported as "N/A" by lm-sensors package.
>
> Signed-off-by: Pali Rohár <pali.rohar@gmail.com>
> ---
> drivers/char/i8k.c | 16 ++++++++++------
> 1 file changed, 10 insertions(+), 6 deletions(-)
>
> diff --git a/drivers/char/i8k.c b/drivers/char/i8k.c
> index 7272b08..e34a019 100644
> --- a/drivers/char/i8k.c
> +++ b/drivers/char/i8k.c
> @@ -298,7 +298,7 @@ static int i8k_get_temp(int sensor)
> int temp;
>
> #ifdef I8K_TEMPERATURE_BUG
> - static int prev[4];
> + static int prev[4] = { I8K_MAX_TEMP+1, I8K_MAX_TEMP+1, I8K_MAX_TEMP+1, I8K_MAX_TEMP+1 };
> #endif
> regs.ebx = sensor & 0xff;
> rc = i8k_smm(&regs);
> @@ -317,10 +317,12 @@ static int i8k_get_temp(int sensor)
> */
> if (temp > I8K_MAX_TEMP) {
> temp = prev[sensor];
> - prev[sensor] = I8K_MAX_TEMP;
> + prev[sensor] = I8K_MAX_TEMP+1;
> } else {
> prev[sensor] = temp;
> }
> + if (temp > I8K_MAX_TEMP)
> + return -ERANGE;

Can we return -ENODATA in this case ? I think that would be more appropriate.

> #endif
>
> return temp;
> @@ -499,6 +501,8 @@ static ssize_t i8k_hwmon_show_temp(struct device *dev,
> int temp;
>
> temp = i8k_get_temp(index);
> + if (temp == -ERANGE)
> + return -EINVAL;

and can we also return -ENODATA to user space ?
This would make the code a bit cleaner.

Thanks,
Guenter



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