[Skiboot] [PATCH 2/2] sensors: occ: Fix a bug when sensor values are zero

[Vaidyanathan Srinivasan]

* Gautham R Shenoy <ego at linux.vnet.ibm.com> [2020-04-24 12:11:15]:

> From: "Gautham R. Shenoy" <ego at linux.vnet.ibm.com>
> 
> The commit 1b9a449d ("opal-api: add endian conversions to most opal
> calls") modified the code in opal_read_sensor() to make it
> Little-Endian safe. In the process, it changed the code so that if a
> sensor value was zero, it would simply return OPAL_SUCCESS without
> updating the return buffer. As a result, the return buffer contained
> bogus values which were reflected on those sensors being read by the
> Kernel.
> 
> This patch fixes it by ensuring that the return buffer is updated with
> the value read from the sensor every time.
> 
> Thanks to Vaidyanathan Srinivasan <svaidy at linux.vnet.ibm.com> for
> spotting the missing return-buffer update.
> 
> Fixes: commit 1b9a449d ("opal-api: add endian conversions to most opal
> calls")
> Reported-by: Pavaman Subramaniyam <pavsubra at in.ibm.com>
> Tested-by: Pavaman Subramaniyam <pavsubra at in.ibm.com>
> Signed-off-by: Gautham R. Shenoy <ego at linux.vnet.ibm.com>

Reviewed-by: Vaidyanathan Srinivasan <svaidy at linux.ibm.com>


> ---
>  hw/occ-sensor.c | 3 ++-
>  1 file changed, 2 insertions(+), 1 deletion(-)
> 
> diff --git a/hw/occ-sensor.c b/hw/occ-sensor.c
> index a5d0974..76d63f3 100644
> --- a/hw/occ-sensor.c
> +++ b/hw/occ-sensor.c
> @@ -276,7 +276,7 @@ int occ_sensor_read(u32 handle, __be64 *data)
> 
>  	d = read_sensor(buff, attr);
>  	if (!d)
> -		return OPAL_SUCCESS;
> +		goto out_success;
> 
>  	md = get_names_block(hb);
>  	if (be16_to_cpu(md[id].type) == OCC_SENSOR_TYPE_POWER && attr == SENSOR_ACCUMULATOR)
> @@ -284,6 +284,7 @@ int occ_sensor_read(u32 handle, __be64 *data)
>  	else
>  		scale_sensor(&md[id], &d);
> 
> +out_success:
>  	*data = cpu_to_be64(d);
> 
>  	return OPAL_SUCCESS;

Perfect and working fix for a subtle bug :)

Thanks,
Vaidy