Re: [PATCH] i8k: Fix temperature bug handling in i8k_get_temp()

[Guenter Roeck]

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.ro...@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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