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[2620:137:e000::1:20]) by mx.google.com with ESMTP id lv9-20020a170906bc8900b0099272ea3a68si7178753ejb.780.2023.07.13.01.23.33; Thu, 13 Jul 2023 01:23:58 -0700 (PDT) Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 2620:137:e000::1:20 as permitted sender) client-ip=2620:137:e000::1:20; Authentication-Results: mx.google.com; dkim=pass header.i=@bootlin.com header.s=gm1 header.b=jsPq8HwZ; spf=pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 2620:137:e000::1:20 as permitted sender) smtp.mailfrom=linux-kernel-owner@vger.kernel.org; dmarc=pass (p=REJECT sp=REJECT dis=NONE) header.from=bootlin.com Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S233014AbjGMHzR (ORCPT + 99 others); Thu, 13 Jul 2023 03:55:17 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:35858 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S232648AbjGMHzM (ORCPT ); Thu, 13 Jul 2023 03:55:12 -0400 Received: from relay6-d.mail.gandi.net (relay6-d.mail.gandi.net [217.70.183.198]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id DF22C10FA for ; Thu, 13 Jul 2023 00:55:10 -0700 (PDT) Received: by mail.gandi.net (Postfix) with ESMTPSA id E0033C0005; Thu, 13 Jul 2023 07:55:08 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=bootlin.com; s=gm1; t=1689234909; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version: content-transfer-encoding:content-transfer-encoding; bh=zelVWeNXzGogS3y0N3CrG89Tb56cbqeZuO00/dwNJ+E=; b=jsPq8HwZejgrL8khSpcVxtlSAlyB5elFBtvinWqCa27rn35iA3l0jwQLYPPCF4dFNvv0sH fc4b5GgFs8xu35gnhqIceuLJ/FKgvVnxU7hcvIblMpUaEoYdMA6EWoNKYZv4bPcEhyh735 OHGt9MKOAMoMQSCgwAa0J5IH2A4dV++oieSkvltJ1HJ2xW50H963szrSspEb7ocbqfOhAu hiR2s1uK/4hSaXOJ04fBxSrYCqd0OUqHxUCvX/DX00kxpzQ7h+NGrECYnG4Ic1fi23IMgu jtP9/KpiDhNQq5Wo0pLzLEie5v0a/dILa0A75SI5bZ9/ANfvzt/G5FCNhg0tyg== From: Miquel Raynal To: Srinivas Kandagatla , Greg Kroah-Hartman , Cc: Thomas Petazzoni , Robert Marko , Luka Perkov , Miquel Raynal Subject: [PATCH RESEND v5 0/3] NVMEM cells in sysfs Date: Thu, 13 Jul 2023 09:55:04 +0200 Message-Id: <20230713075508.485072-1-miquel.raynal@bootlin.com> X-Mailer: git-send-email 2.34.1 MIME-Version: 1.0 X-GND-Sasl: miquel.raynal@bootlin.com X-Spam-Status: No, score=-2.1 required=5.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,DKIM_VALID_EF,RCVD_IN_DNSWL_BLOCKED, RCVD_IN_MSPIKE_H5,RCVD_IN_MSPIKE_WL,SPF_HELO_PASS,SPF_PASS, T_SCC_BODY_TEXT_LINE autolearn=ham autolearn_force=no version=3.4.6 X-Spam-Checker-Version: SpamAssassin 3.4.6 (2021-04-09) on lindbergh.monkeyblade.net Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org X-getmail-retrieved-from-mailbox: INBOX X-GMAIL-THRID: 1771292997296207682 X-GMAIL-MSGID: 1771292997296207682 Hello, As part of a previous effort, support for dynamic NVMEM layouts was brought into mainline, helping a lot in getting information from NVMEM devices at non-static locations. One common example of NVMEM cell is the MAC address that must be used. Sometimes the cell content is mainly (or only) useful to the kernel, and sometimes it is not. Users might also want to know the content of cells such as: the manufacturing place and date, the hardware version, the unique ID, etc. Two possibilities in this case: either the users re-implement their own parser to go through the whole device and search for the information they want, or the kernel can expose the content of the cells if deemed relevant. This second approach sounds way more relevant than the first one to avoid useless code duplication, so here is a series bringing NVMEM cells content to the user through sysfs. Here is a real life example with a Marvell Armada 7040 TN48m switch: $ nvmem=/sys/bus/nvmem/devices/1-00563/ $ for i in `ls -1 $nvmem/cells/*`; do basename $i; hexdump -C $i | head -n1; done country-code 00000000 54 57 |TW| crc32 00000000 bb cd 51 98 |..Q.| device-version 00000000 02 |.| diag-version 00000000 56 31 2e 30 2e 30 |V1.0.0| label-revision 00000000 44 31 |D1| mac-address 00000000 18 be 92 13 9a 00 |......| manufacture-date 00000000 30 32 2f 32 34 2f 32 30 32 31 20 31 38 3a 35 39 |02/24/2021 18:59| manufacturer 00000000 44 4e 49 |DNI| num-macs 00000000 00 40 |.@| onie-version 00000000 32 30 32 30 2e 31 31 2d 56 30 31 |2020.11-V01| platform-name 00000000 38 38 46 37 30 34 30 2f 38 38 46 36 38 32 30 |88F7040/88F6820| product-name 00000000 54 4e 34 38 4d 2d 50 2d 44 4e |TN48M-P-DN| serial-number 00000000 54 4e 34 38 31 50 32 54 57 32 30 34 32 30 33 32 |TN481P2TW2042032| vendor 00000000 44 4e 49 |DNI| Here is a list of known limitations though: * It is currently not possible to know whether the cell contains ASCII or binary data, so by default all cells are exposed in binary form. * For now the implementation focuses on the read aspect. Technically speaking, in some cases, it could be acceptable to write the cells, I guess, but for now read-only files sound more than enough. A writable path can be added later anyway. * The sysfs entries are created when the device probes, not when the NVMEM driver does. This means, if an NVMEM layout is used *and* compiled as a module *and* not installed properly in the system (a usermode helper tries to load the module otherwise), then the sysfs cells won't appear when the layout is actually insmod'ed because the sysfs folders/files have already been populated. Resending v5: * I forgot the mailing list in my former submission, both are absolutely identical otherwise. Changes in v5: * Rebased on last -rc1, fixing a conflict and skipping the first two patches already taken by Greg. * Collected tags from Greg. * Split the nvmem patch into two, one which just moves the cells creation and the other which adds the cells. Changes in v4: * Use a core helper to count the number of cells in a list. * Provide sysfs attributes a private member which is the entry itself to avoid the need for looking up the nvmem device and then looping over all the cells to find the right one. Changes in v3: * Patch 1 is new: fix a style issue which bothered me when reading the core. * Patch 2 is new: Don't error out when an attribute group does not contain any attributes, it's easier for developers to handle "empty" directories this way. It avoids strange/bad solutions to be implemented and does not cost much. * Drop the is_visible hook as it is no longer needed. * Stop allocating an empty attribute array to comply with the sysfs core checks (this check has been altered in the first commits). * Fix a missing tab in the ABI doc. Changes in v2: * Do not mention the cells might become writable in the future in the ABI documentation. * Fix a wrong return value reported by Dan and kernel test robot. * Implement .is_bin_visible(). * Avoid overwriting the list of attribute groups, but keep the cells attribute group writable as we need to populate it at run time. * Improve the commit messages. * Give a real life example in the cover letter. Miquel Raynal (3): ABI: sysfs-nvmem-cells: Expose cells through sysfs nvmem: core: Create all cells before adding the nvmem device nvmem: core: Expose cells through sysfs Documentation/ABI/testing/sysfs-nvmem-cells | 19 ++++ drivers/nvmem/core.c | 113 ++++++++++++++++++-- 2 files changed, 126 insertions(+), 6 deletions(-) create mode 100644 Documentation/ABI/testing/sysfs-nvmem-cells