From nobody Tue Feb 10 05:26:44 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 A05E4EB64DA for ; Wed, 14 Jun 2023 06:31:29 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S232425AbjFNGb1 (ORCPT ); Wed, 14 Jun 2023 02:31:27 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:44090 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S234706AbjFNGaq (ORCPT ); Wed, 14 Jun 2023 02:30:46 -0400 Received: from relay9-d.mail.gandi.net (relay9-d.mail.gandi.net [IPv6:2001:4b98:dc4:8::229]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 96F30268F for ; Tue, 13 Jun 2023 23:30:24 -0700 (PDT) X-GND-Sasl: miquel.raynal@bootlin.com DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=bootlin.com; s=gm1; t=1686724223; 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=G/EwV9fvhxkTVfX06ik2E/XNt0KK6UdwlK2n4zvpmA8=; b=LJiGsaeJLqYbqWrjDyxjDMkbMxs8VerzVfS/wkB3jcX9/7CAkYp8LJ4euYBsAfJ/qZn5/X 5KS4ceAy6KI2qwSaA0aS5yO8m3ESwCH8zfCoNu1rCf9SG4EMlwfTj4twJnbREovIhDDAs2 sFiXh800vE0DnSiAgkM2HZFctu8IefudxGK3Y0fW5hN7g+WfjKPDc//+49gKf/jcCZNFup xU9WBWEnYtliqZF67GfL9rDvdg1b1R0TcQLuNFLG56UsvFvmcdHjimmTTL0Ae14ZCoYoDD oLjRSp6R66lx7/BX2jekr376g5vfj0JL1dD6kZ8fcgll6xe1NXG6KCia8GMu1g== X-GND-Sasl: miquel.raynal@bootlin.com X-GND-Sasl: miquel.raynal@bootlin.com X-GND-Sasl: miquel.raynal@bootlin.com X-GND-Sasl: miquel.raynal@bootlin.com X-GND-Sasl: miquel.raynal@bootlin.com X-GND-Sasl: miquel.raynal@bootlin.com X-GND-Sasl: miquel.raynal@bootlin.com Received: by mail.gandi.net (Postfix) with ESMTPSA id 5C881FF813; Wed, 14 Jun 2023 06:30:22 +0000 (UTC) From: Miquel Raynal To: Srinivas Kandagatla Cc: Greg Kroah-Hartman , "Rafael J . Wysocki" , , Thomas Petazzoni , Luka Perkov , Robert Marko , Miquel Raynal Subject: [PATCH v4 4/4] nvmem: core: Expose cells through sysfs Date: Wed, 14 Jun 2023 08:30:18 +0200 Message-Id: <20230614063018.2419043-5-miquel.raynal@bootlin.com> X-Mailer: git-send-email 2.34.1 In-Reply-To: <20230614063018.2419043-1-miquel.raynal@bootlin.com> References: <20230614063018.2419043-1-miquel.raynal@bootlin.com> MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable 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. There is one limitation though: if a layout is built as a module but is not properly installed in the system and loaded manually with insmod while the nvmem device driver was built-in, the cells won't appear in sysfs. But if done like that, the cells won't be usable by the built-in kernel drivers anyway. Signed-off-by: Miquel Raynal --- drivers/nvmem/core.c | 109 +++++++++++++++++++++++++++++++++++++++++-- 1 file changed, 105 insertions(+), 4 deletions(-) diff --git a/drivers/nvmem/core.c b/drivers/nvmem/core.c index 342cd380b420..baa1f0038b28 100644 --- a/drivers/nvmem/core.c +++ b/drivers/nvmem/core.c @@ -325,6 +325,43 @@ 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 { @@ -346,8 +383,14 @@ 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, + &nvmem_cells_group, NULL, }; =20 @@ -406,6 +449,58 @@ 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)) + 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_kstrdup(&nvmem->dev, entry->name, GFP_KERNEL= ); + 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; + +unlock_mutex: + mutex_unlock(&nvmem_mutex); + + return ret; +} + #else /* CONFIG_NVMEM_SYSFS */ =20 static int nvmem_sysfs_setup_compat(struct nvmem_device *nvmem, @@ -976,16 +1071,22 @@ struct nvmem_device *nvmem_register(const struct nvm= em_config *config) if (rval) goto err_remove_cells; =20 + rval =3D nvmem_add_cells_from_layout(nvmem); + if (rval) + goto err_remove_cells; + +#ifdef CONFIG_NVMEM_SYSFS + rval =3D nvmem_populate_sysfs_cells(nvmem); + if (rval) + goto err_remove_cells; +#endif + dev_dbg(&nvmem->dev, "Registering nvmem device %s\n", config->name); =20 rval =3D device_add(&nvmem->dev); if (rval) goto err_remove_cells; =20 - rval =3D nvmem_add_cells_from_layout(nvmem); - if (rval) - goto err_remove_cells; - blocking_notifier_call_chain(&nvmem_notifier, NVMEM_ADD, nvmem); =20 return nvmem; --=20 2.34.1