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[199.106.103.254]) by smtp.gmail.com with ESMTPSA id a92af1059eb24-1b3b5b1003fsm16392776c88.6.2026.11.11.10.39.24 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 11 Nov 2026 10:39:26 -0800 (PST) Date: Wed, 11 Nov 2026 10:39:20 -0800 From: Jonathan Cameron To: Cristian Marussi Cc: linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org, arm-scmi@vger.kernel.org, linux-doc@vger.kernel.org, sudeep.holla@kernel.org, james.quinlan@broadcom.com, f.fainelli@gmail.com, vincent.guittot@linaro.org, etienne.carriere@st.com, peng.fan@oss.nxp.com, michal.simek@amd.com, d-gole@ti.com, elif.topuz@arm.com, lukasz.luba@arm.com, philip.radford@arm.com, david@kernel.org, souvik.chakravarty@arm.com, leitao@kernel.org, kas@kernel.org, puranjay@kernel.org, usama.arif@linux.dev, kernel-team@meta.com Subject: Re: [PATCH v15 00/35] Introduce SCMI Telemetry support Message-ID: <20261111103920.00004f75@oss.qualcomm.com> In-Reply-To: References: <20261109091221.2532706-1-cristian.marussi@arm.com> <20261110163809.000070d6@oss.qualcomm.com> Organization: Qualcomm X-Mailer: Claws Mail 4.4.0 (GTK 3.24.51; x86_64-w64-mingw32) X-Mailing-List: linux-doc@vger.kernel.org List-Id: List-Post: List-Help: List-Subscribe: List-Unsubscribe: List-Owner: Precedence: list MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit X-Proofpoint-Spam-Details-Enc: AW1haW4tMjYxMTExMDA3NCBTYWx0ZWRfX3tXtk+2G0A+0 24vv6njoW92M/3QToDQxqzWq5Det+jCfAF0i5DXBF68vUSoq2dbmmDv597oAs5nPm2mKWIk19Xz ZjzzzOqxFRT4qOP7LPmpuBsTerzxJLqJ4KDxVf1zyRkleMUo5YtXzdVrgu7NlRt+w3eKHrhNU0D D2j5/U0xEIHrsuy+4a/RsaNOubia/PwrcsHIbKr3MwECoSbeyDcZcVmSDOWhkEPbOVNdyD5F0iD 7GUlP1h6t7vTSqWe/gNQKNTEdA0+HT/5O0fq+NN1zH5CBvLX89fpuRtZgTvYpkHc+Kf82ntGNQg WOCZJJU4JYDEW4nAeYv+XkxYDhNQDSCVqQOOo5A6sFgfSNhkoK2vMPZmPrUl035YyWRjieu4hkj f36KZ/KZ2M4PtI/OsQ4lAZIByMX0H8JCzL3RJ0dpC8Vjr1kmG66Oxb83O2fdxz/4Pro1RkNAEBO ORKkng2IzCmEEWEHYWA== X-Proofpoint-ORIG-GUID: n5GkTos0xTKA7z0fPyuCGjbyHCD6BEoh X-Authority-Analysis: v=2.4 cv=FeuiV5+6 c=1 sm=1 tr=0 ts=6af4b660 cx=c_pps a=kVLUcbK0zfr7ocalXnG1qA==:117 a=JYp8KDb2vCoCEuGobkYCKw==:17 a=kj9zAlcOel0A:10 a=zJRp6_cAMcgA:10 a=s4-Qcg_JpJYA:10 a=VkNPw1HP01LnGYTKEx00:22 a=u7WPNUs3qKkmUXheDGA7:22 a=rJkE3RaqiGZ5pbrm-msn:22 a=7CQSdrXTAAAA:8 a=XOA6F6MpoYfF4Vds9coA:9 a=CjuIK1q_8ugA:10 a=vr4QvYf-bLy2KjpDp97w:22 a=a-qgeE7W1pNrGK8U0ZQC:22 X-Proofpoint-GUID: n5GkTos0xTKA7z0fPyuCGjbyHCD6BEoh X-Proofpoint-Spam-Info: AW1haW4tMjYxMTExMDA3NCBTYWx0ZWRfXz66fyjKQfxJX zsXBEPLeq1xVgwEYk1zd7YC+eUuoZsKVIIgpeSnxHbKtD6v5jeqO+wevvMuEVM+42ZNTxf3Ebm6 MCwhjJc88KIVDg5E2uvIBVoGU1tfOQs= X-Proofpoint-Virus-Version: vendor=baseguard engine=ICAP:2.0.293,Aquarius:18.0.1176,Hydra:6.1.138,FMLib:17.12.100.49 definitions=2026-11-11_05,2026-11-11_03,2025-10-01_01 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 spamscore=0 phishscore=0 priorityscore=1501 lowpriorityscore=0 adultscore=0 clxscore=1015 bulkscore=0 impostorscore=0 malwarescore=0 suspectscore=0 classifier=typeunknown authscore=0 authtc= authcc= route=outbound adjust=0 reason=mlx scancount=1 engine=8.22.0-2611040001 definitions=main-2611110074 On Wed, 11 Nov 2026 10:15:16 +0000 Cristian Marussi wrote: > On Tue, Nov 10, 2026 at 04:38:09PM -0800, Jonathan Cameron wrote: > > > The upcoming SCMI v4.0 specification [0] introduces a new SCMI protocol > > > dedicated to System Telemetry. > > > > > > > Hi Cristian, > > Hi Jonathan, > > thanks for your time...I sincerely hope you're travelling abroad on some > remote timezone given the time these reviews came in :D I'm based in Pacific time these days so was only 4pm ;) > > > > > So, the main issue here is pretty much summarized by: > > > > 28 files changed, 12801 insertions(+), 99 deletions(-) > > (obviously there are tests etc, but it's still > 10k lines) > > > > Usually I try to implement the complete set of features of a new protocol > but indeed this new Telemetry thing is huge by itself so it became quickly > overwhelming to review...imagine to code and test it. > > > There are relatively few reviewers who would even consider taking that on. > > I foolishly thought it wouldn't be too bad (and I review a lot of code). > > By about 3/4 of the way though, probably much earlier, I know the quality > > of review went down considerably. Honestly it was probably a waste of > > time continuing but I'm stubborn like that. > > > > So, unless you have a path to bribing or sweet talking various folk to > > deal with reviewing this with each having to set aside multiple days > > to do it, likely repeating for a couple of versions yet, I think you've > > got to figure out out how to make the first patch set more manageable. > > Probably don't split it up as much as the mpam or CCA folk have had to, > > but you have a lot of colleagues who are experiencing the same problem > > at the moment. They may be able to advise. > > > > So it would be nice if what was in that first patch set was 'functional' > > but I don't think it needs to function on every systems or support more > > than an absolutely minimal feature set. Just fail to probe when you see > > something that isn't supported by that minimal set if that means > > the thing won't be functional. > > > > Once that's in place, over a couple of additional patch sets you can > > get to everything you have here. > > > > So what if you choose one data path (shmti perhaps), no notifications, > > events, maybe even simplify to one of the readback paths. > > Maybe even drop event groups initially. > > Based on our real world initial customer of this I can certainly drop a > few features that are not supported anyway by the real FW and move it to > a later patchset, stuff like groups, notifications and single sample > reads, but all of the rest is hardly removable while keeping the system > functional and usable. For purposes of upstream. I'm not sure we care if a particular implementation is useable with the feature set initially supported. We just care if there is a path to test the subset supported (hacks / emulation, whatever is fine). > > > Possibly even drop timestamps. Definitely drop things like boot-on > > support and debugfs (unless you are using that as a cheeky 'functional' > > test ahead of the main userspace interface. > > Not sure what you mean by drop timestamps, definitelly cannot drop > boot-on (it is how systems are configured indeed) neither debugfs used > for bring-up and FW debug. Timestamp variety is complex. Fairly sure you are allowed to report no timestamps at all as one option. If you pretend they all look like that initially it might bring some simplifications. Anyhow, you know this code better than I do, so maybe that is harder than I'm thinking. I'd still push boot-on out for a follow on patch set. Sure can aim to land that one quickly! Sure customers will get irritated by lack of support for what they have. Taking equivalent of MPAM. The initial support for that covered pretty much nothing on real platforms. Customers were (and still are) irritated. But that allowed progress in the right direction. > > > > > How much would that slim things down? It doesn't even have to be > > useful, just testable. Realistically I think the hope of getting > > enough review doubles if you can halve the size of what you are asking > > people to look at. > > I am not sure how many lines I can shed with the above features drops but > I'll give it a go anyway at slimming down the series after I have gone > through this round of Sashiko pains. If we have to fallback to breaking it into steps that don't do much more than print a message to say 'stuff found' then do that. It's ugly but MPAM did that, RME is doing that. No one likes dead code, but it does allow progress to be made. Ideal is end to end with subset of features then add features but not always achievable. Normal rule of thumb for landing a feature is sub 2k lines of code because that is about what a reviewer can digest in one go. Very rare anything above 5k makes progress. As Sudeep mentioned, a lot of folk will open the cover letter, see loc and close it again unread. Jonathan