Re: [PATCH v2 1/2] cfg80211: Add support to set tx power for a station associated

[Ben Greear <greearb@candelatech.com>]

On 02/01/2017 09:57 AM, Ashok Raj Nagarajan wrote:
> On 2017-02-01 23:06, Ben Greear wrote:
>> On 02/01/2017 09:27 AM, Ashok Raj Nagarajan wrote:
>>
>>>>> +static int nl80211_parse_sta_txpower_setting(struct genl_info *info,
>>>>> +                         struct station_parameters *params)
>>>>> +{
>>>>> +    struct cfg80211_registered_device *rdev = info->user_ptr[0];
>>>>> +    enum nl80211_tx_power_setting type;
>>>>> +    int idx;
>>>>> +
>>>>> +    if (!rdev->ops->set_tx_power ||
>>>>> +        !wiphy_ext_feature_isset(&rdev->wiphy,
>>>>> +                     NL80211_EXT_FEATURE_STA_TX_PWR))
>>>>> +        return -EOPNOTSUPP;
>>>>
>>>> Maybe always let a user set to default value even if the driver does not
>>>> support setting specific values?
>>>>
>>>
>>> IMHO, having some default value in place of non-valid values may not be the right way.
>>
>> If a user or user-space script wants to always be able to initialize
>> things to default
>> values, it would be nice if it did not have to pay specific attention
>> to whether the
>> NIC supports STA_TX_PWR feature or not.  Since a NIC that does not
>> support this feature will always
>> have sta TX power set to default by definition, that is why I think
>> you should let
>> the call succeed in that case.
>>
>
> I think it would be better/easier to handle the error cases in the user-space scripts than at the driver here, no? NIC that doesn't support this feature will
> set the tx power to the station depending on the rate algorithm in place. So the same NIC and same station will have different txpower depending on the
> environment? On the other hand, how do we decide what constant (?) default value to be sent to userspace?

You use value '0' to mean set to default values, as far as I can tell.

So, always let a user set the value to 0, regardless of whether STA_RX_PWR feature exists or not.

If you are querying for a value to show user-space, return '0' in this case.

If user tries to set the value to non-zero, then it should fail with EOPNOTSUPP in case STA_TX_PWR
feature does not exist.

Thanks,
Ben



-- 
Ben Greear <greearb@candelatech.com>
Candela Technologies Inc  http://www.candelatech.com


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