From nobody Tue Feb 10 01:59:33 2026 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 8FCA9C0015E for ; Tue, 1 Aug 2023 18:22:16 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S232430AbjHASWP (ORCPT ); Tue, 1 Aug 2023 14:22:15 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:37504 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231994AbjHASVv (ORCPT ); Tue, 1 Aug 2023 14:21:51 -0400 Received: from relay4-d.mail.gandi.net (relay4-d.mail.gandi.net [IPv6:2001:4b98:dc4:8::224]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id DC8AF269A for ; Tue, 1 Aug 2023 11:21:49 -0700 (PDT) Received: by mail.gandi.net (Postfix) with ESMTPSA id F359FE0005; Tue, 1 Aug 2023 18:21:46 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=bootlin.com; s=gm1; t=1690914108; 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: in-reply-to:in-reply-to:references:references; bh=wZXUbb+s305f0R0d6PSBqvTxl9Ubms9zy8HvCNQc7YE=; b=nOLMpLd4UInlbOOe3sFtYzpGem4yyavZiwBoz/6dbG4a60Njd723o1505zRpf2hWpTMcVb zg15v8iyqGn7ktDGmZw6tCI4ci1ILSP/0huHmt62q2mA/e1Wn+UNB1v5KRwK5GTSHbJmtP 2vIPc7RUgXBa5XtSrzqrG4Op/HzAyyedPXtNblcYej90xCSfnHg2UkLrQZOkiqzz5sefr0 IgQBGNUI9ut0dA5k3Zks2HDScjRV3V9fn0G3bH/aOblr87Dpivu2YMMIo5ThMNM06FPnp8 Moqn9kLD1MpIRWV+acaGQpgAeqlM1HCHdTzlIjWquR6poU4siWbMI1BpZnWDUA== From: Miquel Raynal To: Srinivas Kandagatla Cc: Greg Kroah-Hartman , Thomas Petazzoni , Robert Marko , Luka Perkov , Michael Walle , , Randy Dunlap , Chen-Yu Tsai , Daniel Golle , =?UTF-8?q?Rafa=C5=82=20Mi=C5=82ecki?= , Miquel Raynal Subject: [PATCH v7 7/7] nvmem: core: Expose cells through sysfs Date: Tue, 1 Aug 2023 20:21:32 +0200 Message-Id: <20230801182132.1058707-8-miquel.raynal@bootlin.com> X-Mailer: git-send-email 2.34.1 In-Reply-To: <20230801182132.1058707-1-miquel.raynal@bootlin.com> References: <20230801182132.1058707-1-miquel.raynal@bootlin.com> MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable X-GND-Sasl: miquel.raynal@bootlin.com Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Type: text/plain; charset="utf-8" The binary content of nvmem devices is available to the user so in the easiest cases, finding the content of a cell is rather easy as it is just a matter of looking at a known and fixed offset. However, nvmem layouts have been recently introduced to cope with more advanced situations, where the offset and size of the cells is not known in advance or is dynamic. When using layouts, more advanced parsers are used by the kernel in order to give direct access to the content of each cell, regardless of its position/size in the underlying device. Unfortunately, these information are not accessible by users, unless by fully re-implementing the parser logic in userland. Let's expose the cells and their content through sysfs to avoid these situations. Of course the relevant NVMEM sysfs Kconfig option must be enabled for this support to be available. Not all nvmem devices expose cells. Indeed, the .bin_attrs attribute group member will be filled at runtime only when relevant and will remain empty otherwise. In this case, as the cells attribute group will be empty, it will not lead to any additional folder/file creation. Exposed cells are read-only. There is, in practice, everything in the core to support a write path, but as I don't see any need for that, I prefer to keep the interface simple (and probably safer). The interface is documented as being in the "testing" state which means we can later add a write attribute if though relevant. Signed-off-by: Miquel Raynal --- drivers/nvmem/core.c | 113 +++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 113 insertions(+) diff --git a/drivers/nvmem/core.c b/drivers/nvmem/core.c index 868a6f8b3227..beecb30a1642 100644 --- a/drivers/nvmem/core.c +++ b/drivers/nvmem/core.c @@ -330,6 +330,43 @@ static umode_t nvmem_bin_attr_is_visible(struct kobjec= t *kobj, return nvmem_bin_attr_get_umode(nvmem); } =20 +static struct nvmem_cell *nvmem_create_cell(struct nvmem_cell_entry *entry, + const char *id, int index); + +static ssize_t nvmem_cell_attr_read(struct file *filp, struct kobject *kob= j, + struct bin_attribute *attr, char *buf, + loff_t pos, size_t count) +{ + struct nvmem_cell_entry *entry; + struct nvmem_cell *cell =3D NULL; + size_t cell_sz, read_len; + void *content; + + entry =3D attr->private; + cell =3D nvmem_create_cell(entry, entry->name, 0); + if (IS_ERR(cell)) + return PTR_ERR(cell); + + if (!cell) + return -EINVAL; + + content =3D nvmem_cell_read(cell, &cell_sz); + if (IS_ERR(content)) { + read_len =3D PTR_ERR(content); + goto destroy_cell; + } + + read_len =3D min_t(unsigned int, cell_sz - pos, count); + memcpy(buf, content + pos, read_len); + kfree(content); + +destroy_cell: + kfree_const(cell->id); + kfree(cell); + + return read_len; +} + /* default read/write permissions */ static struct bin_attribute bin_attr_rw_nvmem =3D { .attr =3D { @@ -351,11 +388,21 @@ static const struct attribute_group nvmem_bin_group = =3D { .is_bin_visible =3D nvmem_bin_attr_is_visible, }; =20 +/* Cell attributes will be dynamically allocated */ +static struct attribute_group nvmem_cells_group =3D { + .name =3D "cells", +}; + static const struct attribute_group *nvmem_dev_groups[] =3D { &nvmem_bin_group, NULL, }; =20 +static const struct attribute_group *nvmem_cells_groups[] =3D { + &nvmem_cells_group, + NULL, +}; + static struct bin_attribute bin_attr_nvmem_eeprom_compat =3D { .attr =3D { .name =3D "eeprom", @@ -411,6 +458,64 @@ static void nvmem_sysfs_remove_compat(struct nvmem_dev= ice *nvmem, device_remove_bin_file(nvmem->base_dev, &nvmem->eeprom); } =20 +static int nvmem_populate_sysfs_cells(struct nvmem_device *nvmem) +{ + struct bin_attribute **cells_attrs, *attrs; + struct nvmem_cell_entry *entry; + unsigned int ncells =3D 0, i =3D 0; + int ret =3D 0; + + mutex_lock(&nvmem_mutex); + + if (list_empty(&nvmem->cells)) { + nvmem_cells_group.bin_attrs =3D NULL; + goto unlock_mutex; + } + + /* Allocate an array of attributes with a sentinel */ + ncells =3D list_count_nodes(&nvmem->cells); + cells_attrs =3D devm_kcalloc(&nvmem->dev, ncells + 1, + sizeof(struct bin_attribute *), GFP_KERNEL); + if (!cells_attrs) { + ret =3D -ENOMEM; + goto unlock_mutex; + } + + attrs =3D devm_kcalloc(&nvmem->dev, ncells, sizeof(struct bin_attribute),= GFP_KERNEL); + if (!attrs) { + ret =3D -ENOMEM; + goto unlock_mutex; + } + + /* Initialize each attribute to take the name and size of the cell */ + list_for_each_entry(entry, &nvmem->cells, node) { + sysfs_bin_attr_init(&attrs[i]); + attrs[i].attr.name =3D devm_kasprintf(&nvmem->dev, GFP_KERNEL, + "%s@%x", entry->name, + entry->offset); + attrs[i].attr.mode =3D 0444; + attrs[i].size =3D entry->bytes; + attrs[i].read =3D &nvmem_cell_attr_read; + attrs[i].private =3D entry; + if (!attrs[i].attr.name) { + ret =3D -ENOMEM; + goto unlock_mutex; + } + + cells_attrs[i] =3D &attrs[i]; + i++; + } + + nvmem_cells_group.bin_attrs =3D cells_attrs; + + ret =3D devm_device_add_groups(&nvmem->dev, nvmem_cells_groups); + +unlock_mutex: + mutex_unlock(&nvmem_mutex); + + return ret; +} + #else /* CONFIG_NVMEM_SYSFS */ =20 static int nvmem_sysfs_setup_compat(struct nvmem_device *nvmem, @@ -2148,8 +2253,16 @@ static int nvmem_try_matching_available_layout(struc= t nvmem_device *nvmem) if (ret) goto put_layout; =20 +#ifdef CONFIG_NVMEM_SYSFS + ret =3D nvmem_populate_sysfs_cells(nvmem); + if (ret) + goto del_cells; +#endif + return 0; =20 +del_cells: + nvmem_device_remove_all_cells(nvmem); put_layout: nvmem_layout_put(nvmem->layout); return ret; --=20 2.34.1