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Mon, 14 Sep 2026 13:32:53 -0700 (PDT) X-Received: by 2002:a17:90b:57e7:b0:38e:57a3:f218 with SMTP id 98e67ed59e1d1-39dec05d7femr8511268a91.13.1789417973397; Mon, 14 Sep 2026 13:32:53 -0700 (PDT) Received: from localhost ([50.35.44.179]) by smtp.gmail.com with ESMTPSA id 5a478bee46e88-33bd8ad03ccsm9880610eec.2.2026.09.14.13.32.51 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 14 Sep 2026 13:32:53 -0700 (PDT) Date: Mon, 14 Sep 2026 13:32:49 -0700 From: Jonathan Cameron To: "Aneesh Kumar K.V (Arm)" Cc: linux-coco@lists.linux.dev, linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, Jason Gunthorpe , Catalin Marinas , Greg KH , Jeremy Linton , Jonathan Cameron , Lorenzo Pieralisi , Mark Rutland , Sudeep Holla , Will Deacon , Steven Price , Suzuki K Poulose , Andre Przywara , Sudeep Holla Subject: Re: [PATCH v11 1/7] firmware: smccc: Add an Arm SMCCC bus Message-ID: <20260914133249.00007d35@oss.qualcomm.com> In-Reply-To: <20260914060511.277948-2-aneesh.kumar@kernel.org> References: <20260914060511.277948-1-aneesh.kumar@kernel.org> <20260914060511.277948-2-aneesh.kumar@kernel.org> Organization: Qualcomm X-Mailer: Claws Mail 4.4.0 (GTK 3.24.51; x86_64-w64-mingw32) Precedence: bulk X-Mailing-List: linux-coco@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit X-Authority-Analysis: v=2.4 cv=G+KJgNk5 c=1 sm=1 tr=0 ts=6aa859f6 cx=c_pps a=RP+M6JBNLl+fLTcSJhASfg==:117 a=aNnz9XPx1a4JIXSYt2cE/A==:17 a=kj9zAlcOel0A:10 a=VdqzKS8jKosA:10 a=s4-Qcg_JpJYA:10 a=VkNPw1HP01LnGYTKEx00:22 a=u7WPNUs3qKkmUXheDGA7:22 a=gowsoOTTUOVcmtlkKump:22 a=VwQbUJbxAAAA:8 a=Ikd4Dj_1AAAA:8 a=EUspDBNiAAAA:8 a=rWZSSP1HmsjXzHu-GLMA:9 a=CjuIK1q_8ugA:10 a=iS9zxrgQBfv6-_F4QbHw:22 X-Proofpoint-Spam-Details-Enc: AW1haW4tMjYwOTE0MDI5MyBTYWx0ZWRfXzbmgym4X5bmP vt4RkoEPm6yQaI4Bx8cqJUfW0MsoC8FSPkBct4AR9iF7noaUwX22gaXVO9dDKfnfFYiayC+rFby GwUp/TgRg0yRNuPXBXjhndxc3DC+eOM31V2U11y8Ka0qx0ffnz3u97o72ONQF3trRzZkeiInT4H ulGs74EkNvHuvon+Kk+Gcis4v7hWA5bffEBAysrBRF+j97AGAP8jo22+BtY7EaE2laBzaDMyIRR MRMhIKIiNVL9rzGUKovkhc+wfBFMDfNn/JOGAVIqlVC9E9VBGOhGoXBdLw17Wi5IJ7xhPbiDy3j n0wF9ja60kEFR8K/4QlvLXfGVDcgy36Ig8NUdN6Z5Vt/hmczI5sffzZEJhqo5MdLWYibIDqsHZk kOuK6ZZ8xwzIMPm6MfZTXm49IgnOIoEuQKNm2AnfIXtx9umorBHr72kqfRWtr1686sLxbu1DkNr k8XjQ/xJEpKQLXeL8Kg== X-Proofpoint-GUID: r-8GHgID-JL8TLqzIW6YvJh062mVhxEK X-Proofpoint-ORIG-GUID: r-8GHgID-JL8TLqzIW6YvJh062mVhxEK X-Proofpoint-Spam-Info: AW1haW4tMjYwOTE0MDI5MyBTYWx0ZWRfX+ctyEU/70em1 JqNkFjKi1dSJ07MYN+z2KJI1Q/L2oZT7lQJ/SLT9wsYbI65KSm/e5ZV/U5J9XJgTSLSv0wbI/Dc Z6JnNyWAEgHLkcUJDZOXs4c7E7+2fhk= 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=2026-09-14_04,2026-09-14_02,2025-10-01_01 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 suspectscore=0 bulkscore=0 impostorscore=0 malwarescore=0 clxscore=1011 lowpriorityscore=0 phishscore=0 adultscore=0 priorityscore=1501 spamscore=0 classifier=typeunknown authscore=0 authtc= authcc= route=outbound adjust=0 reason=mlx scancount=1 engine=8.22.0-2609040000 definitions=main-2609140293 On Mon, 14 Sep 2026 11:35:05 +0530 "Aneesh Kumar K.V (Arm)" wrote: > SMCCC-discovered firmware services are currently represented by separate > platform devices, such as smccc_trng and arm-cca-dev. Those devices do not > represent independent DT/ACPI-described platform resources; they are > features of the SMCCC firmware interface. > > Add an Arm SMCCC bus for services discovered through the SMCCC firmware > interface. The bus provides SMCCC device and driver registration helpers, > name-based matching, modalias generation, and a sysfs modalias attribute so > SMCCC service drivers can bind to discovered firmware services and autoload > as modules. > > Follow-up changes can then register SMCCC firmware services as arm-smccc > devices instead of creating independent per-feature platform devices. > > Based on arm_ffa code That code has the same issue as below and for bonus points doesn't check if dev_set_name() succeeds or not. > > Reviewed-by: Jason Gunthorpe > Reviewed-by: Sudeep Holla > Signed-off-by: Aneesh Kumar K.V (Arm) On tiny bit of fragility inline that I'd suggestion avoiding now rather than later. Down to dev_set_name() doing allocations in some cases under the hood that are tricky to tidy up with device_register() being used. With that tidied up Reviewed-by: Jonathan Cameron > diff --git a/drivers/firmware/smccc/bus.c b/drivers/firmware/smccc/bus.c > new file mode 100644 > index 000000000000..caba1a03c997 > --- /dev/null > +++ b/drivers/firmware/smccc/bus.c > + > +struct arm_smccc_device *arm_smccc_device_register(const char *name, u32 func_id) > +{ > + int ret; > + struct arm_smccc_device *smccc_dev; > + > + if (!name) > + return ERR_PTR(-EINVAL); > + > + smccc_dev = kzalloc_obj(*smccc_dev); > + if (!smccc_dev) > + return ERR_PTR(-ENOMEM); > + > + smccc_dev->func_id = func_id; > + smccc_dev->dev.bus = &arm_smccc_bus_type; > + smccc_dev->dev.release = arm_smccc_release_device; > + > + ret = dev_set_name(&smccc_dev->dev, "%s", name); Does protecting the string defeat the nice underlying const handling? e.g. ret = dev_set_name(&smccc_dev->dev, name); might be better. Not particular important - I only noticed because you'd often see this between an device_initialize() and device_add() and then we'd be relying on the device_put() to clean it up. So as this stands this is fragile as any error paths that later get added... > + if (ret) { > + kfree(smccc_dev); > + return ERR_PTR(ret); > + } > + here can't free the name allocation. So I'd just switch this to a split device setup - something like... smccc_dev = kzalloc_obj(*smccc_dev); if (!smccc_dev) return ERR_PTR(-ENOMEM); smccc_dev->func_id = func_id; smccc_dev->dev.bus = &arm_smccc_bus_type; smccc_dev->dev.release = arm_smccc_release_device; device_initialize(&smccc_dev->dev); ret = dev_set_name(&smccc_dev->dev, "%s", name); //up to you whether you care about const string handling. if (ret) { put_device(&smcc_dev->dev); return ret; } ret = device_register(&smccc_dev->dev); if (ret) { put_device(&smccc_dev->dev); return ERR_PTR(ret); } return smccc_dev; > + ret = device_register(&smccc_dev->dev); > + if (ret) { > + put_device(&smccc_dev->dev); > + return ERR_PTR(ret); > + } > + > + return smccc_dev; > +} > +EXPORT_SYMBOL_GPL(arm_smccc_device_register); > + > +void arm_smccc_device_unregister(struct arm_smccc_device *smccc_dev) > +{ > + if (!smccc_dev) > + return; > + > + device_unregister(&smccc_dev->dev); > +} > +EXPORT_SYMBOL_GPL(arm_smccc_device_unregister); > + > +static int __init arm_smccc_bus_init(void) > +{ > + return bus_register(&arm_smccc_bus_type); > +} > +subsys_initcall(arm_smccc_bus_init);