[U-Boot] [PATCH] power: regulator: Add limits checking while setting voltage and current

[Keerthy]

On Thursday 15 September 2016 04:26 PM, Przemyslaw Marczak wrote:
> Hello Keerthy,
>
> On 09/15/2016 10:54 AM, Keerthy wrote:
>> Currently the specific set ops functions are directly
>> called without any check for voltage/current limits for a regulator.
>> Check for them and proceed.
>>
>> Signed-off-by: Keerthy <j-keerthy at ti.com>
>> ---
>>   drivers/power/regulator/regulator-uclass.c | 10 ++++++++++
>>   1 file changed, 10 insertions(+)
>>
>> diff --git a/drivers/power/regulator/regulator-uclass.c
>> b/drivers/power/regulator/regulator-uclass.c
>> index 4434e36..089455e 100644
>> --- a/drivers/power/regulator/regulator-uclass.c
>> +++ b/drivers/power/regulator/regulator-uclass.c
>> @@ -41,6 +41,11 @@ int regulator_get_value(struct udevice *dev)
>>   int regulator_set_value(struct udevice *dev, int uV)
>>   {
>>       const struct dm_regulator_ops *ops = dev_get_driver_ops(dev);
>> +    struct dm_regulator_uclass_platdata *uc_pdata;
>> +
>> +    uc_pdata = dev_get_uclass_platdata(dev);
>> +    if (uV < uc_pdata->min_uV || uV > uc_pdata->max_uV)
>> +        return -EINVAL;
>>         if (!ops || !ops->set_value)
>>           return -ENOSYS;
>> @@ -61,6 +66,11 @@ int regulator_get_current(struct udevice *dev)
>>   int regulator_set_current(struct udevice *dev, int uA)
>>   {
>>       const struct dm_regulator_ops *ops = dev_get_driver_ops(dev);
>> +    struct dm_regulator_uclass_platdata *uc_pdata;
>> +
>> +    uc_pdata = dev_get_uclass_platdata(dev);
>> +    if (uA < uc_pdata->min_uA || uA > uc_pdata->max_uA)
>> +        return -EINVAL;
>>         if (!ops || !ops->set_current)
>>           return -ENOSYS;
>
> Adding those two checks will conflict with "force" option for
> cmd/regulator.c:283.
> There was value range checking in the command's code, but it was left
> unchecked
> for regulator direct calls.
>
> This change is good, but then maybe the "force" option should be removed
> from command,
> or API's prototypes should be updated by force flag argument?
>
> I assumed that this option could be useful for quick over-voltage
> setting (until reboot),
> since usually (min_uV == max_uV) - the voltage can't be changed in any
> range.
>
> The driver should take care about ignore it or not, however probably
> nobody used this.
>
> Of course this could potentially damage the device by wrong use,
> which can be also made by passing the force flag as an argument - by
> mistake.
>
> What do you thing about, update the dm_regulator_ops by:
>
>  - int (*set_value)(struct udevice *dev, int uV, int flag);
>  - int (*set_current)(struct udevice *dev, int uA, int flag);
>
> and also new flag to the present defined:
>
>  - REGULATOR_FLAG_FORCE = 1 << 2
>
> This requires more work, but will provide the functionality in a proper
> way.

I do not know cmd_regulator is the right place to check for min_uV and 
max_uV. dm_regulator_uclass_platdata has both the limits and this i feel 
is a perfectly valid check in generic place else we would be again 
checking for the same condition in every possible regulator specific 
drivers.

As far as the force option is concerned that i believe is more for 
testing and like you said can be implemented by setting a flag.

Just take a simple case of say a driver like mmc which unknowingly 
requests a wrong voltage and the base driver has no check against min 
and max voltages and assuming the regulator driver goes ahead and sets a 
very high voltage. That can be catastrophic right?

>
> Best regards,
>