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[2001:1c00:c32:7800:5bfa:a036:83f0:f9ec]) by smtp.gmail.com with ESMTPSA id a640c23a62f3a-c2458b094c4sm90018966b.22.2026.08.20.07.50.23 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Thu, 20 Aug 2026 07:50:24 -0700 (PDT) Message-ID: <09a17e4f-99cf-406c-9cf0-a237c9f0bb19@oss.qualcomm.com> Date: Thu, 20 Aug 2026 16:50:22 +0200 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [RFC PATCH 2/2] firmware: arm_scmi: Add bus support for autoloading To: Sudeep Holla , Daniel Lezcano , Cristian Marussi , Bjorn Andersson Cc: arm-scmi@vger.kernel.org, guomin_chen@sina.com, linux-arm-kernel@lists.infradead.org, peng.fan@nxp.com, quic_xinqzhan@quicinc.com References: <20250203100154.140877-1-cristian.marussi@arm.com> <20250203100154.140877-2-cristian.marussi@arm.com> <20260609-upbeat-bullfrog-of-enrichment-0f44aa@sudeepholla> <282af085-1669-4d9d-9c1d-2fc232252be0@oss.qualcomm.com> <20260729-optimistic-lemon-myna-a14bbf@sudeepholla> From: Hans de Goede Content-Language: en-US, nl In-Reply-To: <20260729-optimistic-lemon-myna-a14bbf@sudeepholla> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit X-Proofpoint-Spam-Details-Enc: AW1haW4tMjYwODIwMDExMSBTYWx0ZWRfXyiYUhz/rA2uK FSBP2inWba3jJrNr5izP519icEP51XLH5TbBaG4w9fkHXZAL+22rz7MXEG+Uhcl4MumPnwaD/2P BQMgEAf664tnyr30D9LSSx+LyNAhnuDLeDcnTrzwCIwv/ZFsIQxJ4lDeeMK4jcQCNGoIX4bBFlM WMZOuNEhQa5j82s7UmEMo/0BPKovOpl72DXcEIZAPADzM4YuJZbH3BSDd93fPMewPp9sczHAjrR aRbuoWRoDggxw2DAIDJsTh3+fzg+PKFXfHemUZiD0M2LvVVkUDkuo6k3ai9vn/CUYEZU8QMfKAl ZkIUJDl720q3YIkPfqfX7IIyWrxGm0iGMRpFQ3NB5zj6sDUOkPj22HAyzjDOlCvIxFCaGdWfddM mrqTyBUnCF+wobF48fQuC+9+5FeA0lbivoRKastopZQRoEs9WBhZ1x3BexNUTC8rF3FPETB5VOw EkaRJFzbHZckWg250Mw== X-Authority-Analysis: v=2.4 cv=KpJ9H2WN c=1 sm=1 tr=0 ts=6a871434 cx=c_pps a=qKBjSQ1v91RyAK45QCPf5w==:117 a=xqWC_Br6kY4A:10 a=IkcTkHD0fZMA:10 a=Sv0fKeRqtYgA:10 a=s4-Qcg_JpJYA:10 a=VkNPw1HP01LnGYTKEx00:22 a=u7WPNUs3qKkmUXheDGA7:22 a=eoimf2acIAo5FJnRuUoq:22 a=VwQbUJbxAAAA:8 a=EUspDBNiAAAA:8 a=Pb2rOm9Yw1pd37dnyEcA:9 a=QEXdDO2ut3YA:10 a=NFOGd7dJGGMPyQGDc5-O:22 X-Proofpoint-Spam-Info: AW1haW4tMjYwODIwMDExMSBTYWx0ZWRfXyZ2KDkJVtuPg 9MP7oZzF/dZ1RxtHFk0EepQ6mArIooPfjbeU9E4nn4m07gzirCnT8bMHwln7aC3xqv0Z1TJFqXz gIfGD3UYnG6NVDfKVMCHt2mRsr6s3jM= X-Proofpoint-ORIG-GUID: BgKZkOsPcWs9Vp9wGUVxXXpS0d6KfXpx X-Proofpoint-GUID: BgKZkOsPcWs9Vp9wGUVxXXpS0d6KfXpx X-Proofpoint-Virus-Version: vendor=baseguard engine=ICAP:2.0.293,Aquarius:18.0.1176,Hydra:6.1.134,FMLib:17.12.100.49 definitions=2026-08-19_06,2026-08-20_01,2025-10-01_01 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 phishscore=0 adultscore=0 malwarescore=0 lowpriorityscore=0 priorityscore=1501 impostorscore=0 bulkscore=0 suspectscore=0 clxscore=1015 spamscore=0 classifier=typeunknown authscore=0 authtc= authcc= route=outbound adjust=0 reason=mlx scancount=1 engine=8.22.0-2606150000 definitions=main-2608200111 X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.9.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20260820_075029_129941_C6E85DBB X-CRM114-Status: GOOD ( 29.54 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org Hi All, On 29-Jul-26 16:17, Sudeep Holla wrote: > On Wed, Jul 29, 2026 at 04:11:18PM +0200, Daniel Lezcano wrote: >> >> Hi Cristian, >> >> On 6/9/26 11:01, Sudeep Holla wrote: >>> On Mon, Jun 08, 2026 at 05:51:57PM +0100, Cristian Marussi wrote: >> >> [ ... ] >> >>>> Thoughts ? Plans ? Given the internal discussion about this on Slack I decided to look into fixing this and while reading the thread from [1] found a pointer to this thread. >>> Just repost as non-rfc after next merge window and we will see if there is >>> much interest to get it merged for the following one and take it from there. >> >> Are you planning to resend the series ? I can test them on my laptop >> > > I thought [1] from Bjorn was addressing the same issue ? Yes, but it does not solve the chicken and the egg problem we've wrt module auto-loading. It tries to do so in patch 2/2 of the [1] series but that relies on request_module() rather then a proper/normal modalias uevent and that request_module() typically will happen inside the initramfs and then fails if the needed module is not in the initramfs. Normal bus devices with a proper modalias uevent do not suffer from this because there udev does the modprobe based on the uevent file under the device's sysfs dir and it retries this after the switch to the real rootfs. The problem the current scmi code has is that it creates devices under the SCMI bus based on protocol+name pairs in the scmi_requested_devices list. And that list is populated based on driver->id_table entries from any loaded drivers. So for a device to get created the module registering the driver with the matching scmi_device_id-s needs to be loaded first. And the way the device model + udev contract works is that the module will be auto-loaded based on the modalias of the created device. So no module, no device on the scmi bus and no device no module autoloading. Hence chicken and egg. I believe that the first patch from Bjorn's series which is similar but more complete then the first patch from this (Cristian's) series + pre-populating the scmi_requested_devices for Standard protocol devices as Christian's second patch does should do the trick. This break the chicken and egg problem for standard proto devices. This means no auto-loading for modules for custom protocols, there is no way to avoid this. As an exception we could add any custom protocols for which support is added to the mainline kernel to the table used to pre-populate the scmi_requested_devices list. I'll go and prepare a new series consisting of Bjorn's 1/2 (unmodified) + Christian's 2/2 reduced to just pre-populating the table and after testing that that does the trick I'll post that as a v2 series obsoleting both existing series. Regards, Hans [1] https://lore.kernel.org/all/20260618-scmi-modalias-v2-0-8c7547c1be21@oss.qualcomm.com