Received-SPF: pass (google.com: best guess record for domain of linux-kernel-owner@vger.kernel.org designates 209.132.180.67 as permitted sender) client-ip=209.132.180.67;
Subject: Re: [PATCH v2 2/2] hwmon: ibmpowernv: Add attributes to
 enable/disable sensor groups
To:     Shilpasri G Bhat <shilpa.bhat@linux.vnet.ibm.com>,
        mpe@ellerman.id.au
Cc:     linuxppc-dev@lists.ozlabs.org, linux-hwmon@vger.kernel.org,
        linux-kernel@vger.kernel.org, ego@linux.vnet.ibm.com
References: <1530695793-4584-1-git-send-email-shilpa.bhat@linux.vnet.ibm.com>
 <1530695793-4584-3-git-send-email-shilpa.bhat@linux.vnet.ibm.com>
 <e3a013fb-eaf0-8d45-2f23-3be8b3e5640b@roeck-us.net>
 <c7e1272a-c9c8-a120-632f-7693cef3fd22@linux.vnet.ibm.com>
From:   Guenter Roeck <linux@roeck-us.net>
Message-ID: <f0b3384f-02fb-f4f2-0f89-378183a1fad9@roeck-us.net>
Date:   Wed, 4 Jul 2018 14:42:56 -0700
User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:52.0) Gecko/20100101
 Thunderbird/52.8.0
MIME-Version: 1.0
In-Reply-To: <c7e1272a-c9c8-a120-632f-7693cef3fd22@linux.vnet.ibm.com>
Content-Type: text/plain; charset=utf-8; format=flowed
Content-Language: en-US
Content-Transfer-Encoding: 7bit
Sender: linux-kernel-owner@vger.kernel.org
Precedence: bulk

On 07/04/2018 09:53 AM, Shilpasri G Bhat wrote:
> Hi Guenter,
> 
> Thanks for reviewing the patch.
> On 07/04/2018 08:16 PM, Guenter Roeck wrote:
>>> +        /* Disable if last sensor in the group */
>>> +        send_command = true;
>>> +        for (i = 0; i < sg->nr_sensor; i++) {
>>> +            struct sensor_data *sd = sg->sensors[i];
>>> +
>>> +            if (sd->enable) {
>>> +                send_command = false;
>>> +                break;
>>> +            }
>>
>> This is weird. So there are situations where a request to disable
>> a sensor is accepted, but effectively ignored ? Shouldn't that
>> return, say, -EBUSY ?
> 
> This is because we do not support per-sensor enable/disable. We can only
> enable/disable at a sensor-group level.
> 
> This patch follows the semantic to disable a sensor group iff all the sensors
> belonging to that group have been disabled. Otherwise the sensor alone is marked
> to be disabled and returns -ENODATA on reading it.
> 
> And a sensor group will be enabled if any of the sensor in that group is enabled.
> 

In similar situations, where setting one attribute affects others, a common solution
is to make only the first attribute writable and have it affect all the others.
I think that would make sense here as well, and it would be much simpler to implement.

Guenter

> I will make changes to the remaining code according to your suggestion.
> 
> Thanks and Regards,
> Shilpa
> 
> --
> To unsubscribe from this list: send the line "unsubscribe linux-hwmon" in
> the body of a message to majordomo@vger.kernel.org
> More majordomo info at  http://vger.kernel.org/majordomo-info.html
>