Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 2620:137:e000::1:18 as permitted sender) client-ip=2620:137:e000::1:18;
Message-ID: <7d87d5c9-2d16-7574-3c08-04dbfb58d943@linux.ibm.com>
Date:   Wed, 18 May 2022 15:49:57 +0200
MIME-Version: 1.0
User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:91.0) Gecko/20100101
 Thunderbird/91.8.0
Subject: Re: [PATCH v4 1/2] drivers/s390/char: Add Ultravisor io device
Content-Language: en-US
To:     Janosch Frank <frankja@linux.ibm.com>,
        Heiko Carstens <hca@linux.ibm.com>
Cc:     Greg KH <greg@kroah.com>,
        Alexander Gordeev <agordeev@linux.ibm.com>,
        Shuah Khan <shuah@kernel.org>,
        Christian Borntraeger <borntraeger@linux.ibm.com>,
        Claudio Imbrenda <imbrenda@linux.ibm.com>,
        David Hildenbrand <david@redhat.com>,
        Nico Boehr <nrb@linux.ibm.com>, linux-kernel@vger.kernel.org,
        linux-kselftest@vger.kernel.org, kvm@vger.kernel.org
References: <20220510144724.3321985-1-seiden@linux.ibm.com>
 <20220510144724.3321985-2-seiden@linux.ibm.com> <YoTcxhulemnqiUbC@osiris>
 <48550162-0f8c-4b23-dea4-b9060b24eed9@linux.ibm.com>
From:   Steffen Eiden <seiden@linux.ibm.com>
Organization: IBM
In-Reply-To: <48550162-0f8c-4b23-dea4-b9060b24eed9@linux.ibm.com>
Content-Type: text/plain; charset=UTF-8; format=flowed
Content-Transfer-Encoding: 8bit
Precedence: bulk


On 5/18/22 15:45, Janosch Frank wrote:
> On 5/18/22 13:47, Heiko Carstens wrote:
>> On Tue, May 10, 2022 at 02:47:23PM +0000, Steffen Eiden wrote:
>>> diff --git a/drivers/s390/char/Kconfig b/drivers/s390/char/Kconfig
>>> index 6cc4b19acf85..e9b9902abbaf 100644
>>> --- a/drivers/s390/char/Kconfig
>>> +++ b/drivers/s390/char/Kconfig
>>> @@ -100,6 +100,16 @@ config SCLP_OFB
>>>         This option enables the Open-for-Business interface to the s390
>>>         Service Element.
>>> +config S390_UV_UAPI
>>> +    def_tristate y
>>> +    prompt "Ultravisor userspace API"
>>> +    help
>>> +      Selecting exposes parts of the UV interface to userspace
>>> +      by providing a misc character device at /dev/uv.
>>> +      Using IOCTLs one can interact with the UV.
>>> +      The device is only available if the Ultravisor
>>> +      Facility (158) is present.
>>
>> Is there a reason why this is default "y"? If you think this should be
>> compiled into the kernel if used, then why allow to make it a module
>> at all?
>> Instead you could get rid of a couple if lines of code.
> 
> There was a lot of discussion around this already and the "Y" was chosen 
> as auto-loading this is a pain and therefore the SCLP and CHSC-Misc set 
> it to Y and we took that as an example (Steffen spoke to Peter to get 
> guidance).
> 
> I'm sure that we want the possibility to have this as a module. 
> Personally I'd choose "m" over "y" since the module is only useful for a 
> very small amount of users.

I am fine with changing "y" to "m".

Steffen