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Wed, 18 May 2022 13:45:27 +0000 (GMT) Received: from [9.145.45.168] (unknown [9.145.45.168]) by b06wcsmtp001.portsmouth.uk.ibm.com (Postfix) with ESMTP; Wed, 18 May 2022 13:45:27 +0000 (GMT) Message-ID: <48550162-0f8c-4b23-dea4-b9060b24eed9@linux.ibm.com> Date: Wed, 18 May 2022 15:45:27 +0200 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:91.0) Gecko/20100101 Thunderbird/91.8.0 Content-Language: en-US To: Heiko Carstens , Steffen Eiden Cc: Greg KH , Alexander Gordeev , Shuah Khan , Christian Borntraeger , Claudio Imbrenda , David Hildenbrand , Nico Boehr , 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> From: Janosch Frank Subject: Re: [PATCH v4 1/2] drivers/s390/char: Add Ultravisor io device In-Reply-To: Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-TM-AS-GCONF: 00 X-Proofpoint-ORIG-GUID: aHzQbWoMDfk-vwBiUB2ssxDIqzQxyXtN X-Proofpoint-GUID: uEfrS6DjIVrYZO9ueDhA5bJYYpaJRZ3b X-Proofpoint-Virus-Version: vendor=baseguard engine=ICAP:2.0.205,Aquarius:18.0.874,Hydra:6.0.486,FMLib:17.11.64.514 definitions=2022-05-18_05,2022-05-17_02,2022-02-23_01 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 impostorscore=0 suspectscore=0 mlxscore=0 priorityscore=1501 lowpriorityscore=0 adultscore=0 malwarescore=0 mlxlogscore=999 bulkscore=0 clxscore=1015 phishscore=0 spamscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2202240000 definitions=main-2205180079 Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 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.