Re: [PATCH v7 7/7] nvmem: core: Expose cells through sysfs

Re: [PATCH v7 7/7] nvmem: core: Expose cells through sysfs

[kernel test robot]

:::::: 
:::::: Manual check reason: "low confidence static check warning: drivers/nvmem/core.c:2264:1: sparse: sparse: unused label 'del_cells'"
:::::: 

BCC: lkp@intel.com
CC: oe-kbuild-all@lists.linux.dev
In-Reply-To: <20230801182132.1058707-8-miquel.raynal@bootlin.com>
References: <20230801182132.1058707-8-miquel.raynal@bootlin.com>
TO: Miquel Raynal <miquel.raynal@bootlin.com>

Hi Miquel,

kernel test robot noticed the following build warnings:

[auto build test WARNING on char-misc/char-misc-testing]
[also build test WARNING on char-misc/char-misc-next char-misc/char-misc-linus linus/master v6.5-rc5 next-20230808]
[If your patch is applied to the wrong git tree, kindly drop us a note.
And when submitting patch, we suggest to use '--base' as documented in
https://git-scm.com/docs/git-format-patch#_base_tree_information]

url:    https://github.com/intel-lab-lkp/linux/commits/Miquel-Raynal/nvmem-core-Create-all-cells-before-adding-the-nvmem-device/20230802-022331
base:   char-misc/char-misc-testing
patch link:    https://lore.kernel.org/r/20230801182132.1058707-8-miquel.raynal%40bootlin.com
patch subject: [PATCH v7 7/7] nvmem: core: Expose cells through sysfs
:::::: branch date: 7 days ago
:::::: commit date: 7 days ago
config: x86_64-randconfig-x062-20230808 (https://download.01.org/0day-ci/archive/20230809/202308090730.heIvhehR-lkp@intel.com/config)
compiler: gcc-12 (Debian 12.2.0-14) 12.2.0
reproduce: (https://download.01.org/0day-ci/archive/20230809/202308090730.heIvhehR-lkp@intel.com/reproduce)

If you fix the issue in a separate patch/commit (i.e. not just a new version of
the same patch/commit), kindly add following tags
| Reported-by: kernel test robot <lkp@intel.com>
| Closes: https://lore.kernel.org/r/202308090730.heIvhehR-lkp@intel.com/

sparse warnings: (new ones prefixed by >>)
>> drivers/nvmem/core.c:2264:1: sparse: sparse: unused label 'del_cells'
   drivers/nvmem/core.c:83:23: sparse: sparse: symbol 'nvmem_nb' was not declared. Should it be static?

vim +/del_cells +2264 drivers/nvmem/core.c

48c23a411e77cb Miquel Raynal 2023-08-01  2261  
00d059fd6702f0 Miquel Raynal 2023-08-01  2262  	return 0;
00d059fd6702f0 Miquel Raynal 2023-08-01  2263  
48c23a411e77cb Miquel Raynal 2023-08-01 @2264  del_cells:
48c23a411e77cb Miquel Raynal 2023-08-01  2265  	nvmem_device_remove_all_cells(nvmem);
00d059fd6702f0 Miquel Raynal 2023-08-01  2266  put_layout:
00d059fd6702f0 Miquel Raynal 2023-08-01  2267  	nvmem_layout_put(nvmem->layout);
00d059fd6702f0 Miquel Raynal 2023-08-01  2268  	return ret;
00d059fd6702f0 Miquel Raynal 2023-08-01  2269  }
00d059fd6702f0 Miquel Raynal 2023-08-01  2270  

-- 
0-DAY CI Kernel Test Service
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[PATCH v7 0/7] NVMEM cells in sysfs

[Miquel Raynal]

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|

This layout with a cells/ folder containing one file per cell has been
legitimately challenged by John Thomson. I am not against the idea of
having a sub-folder per cell but I did not find a relevant way to do
that so for know I did not change the sysfs organization. If someone
really wants this other layout, please provide a code snipped which I
can integrate.

Here are two limitations:
* 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.

Changes in v7:
* Rework the layouts registration mechanism to use the platform devices
  logic.
* Fix the two issues reported by Daniel Golle and Chen-Yu Tsai, one of
  them consist in suffixing '@<offset>' to the cell name to create the
  sysfs files in order to be sure they are all unique.
* Update the doc.

Changes in v6:
* ABI documentation style fixes reported by Randy Dunlap:
  s|cells/ folder|"cells" folder|
  Missing period at the end of the final note.
  s|Ex::|Example::|
* Remove spurious patch from the previous resubmission.

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 (7):
  nvmem: core: Create all cells before adding the nvmem device
  nvmem: core: Do not open-code existing functions
  nvmem: core: Track the registered devices
  nvmem: core: Notify when a new layout is registered
  nvmem: core: Rework layouts to become platform devices
  ABI: sysfs-nvmem-cells: Expose cells through sysfs
  nvmem: core: Expose cells through sysfs

 Documentation/ABI/testing/sysfs-nvmem-cells |  21 ++
 drivers/nvmem/core.c                        | 269 +++++++++++++++++---
 drivers/nvmem/layouts/onie-tlv.c            |  39 ++-
 drivers/nvmem/layouts/sl28vpd.c             |  39 ++-
 include/linux/nvmem-consumer.h              |   2 +
 include/linux/nvmem-provider.h              |  11 +-
 6 files changed, 328 insertions(+), 53 deletions(-)
 create mode 100644 Documentation/ABI/testing/sysfs-nvmem-cells

-- 
2.34.1

[PATCH v7 7/7] nvmem: core: Expose cells through sysfs

[Miquel Raynal]

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 <miquel.raynal@bootlin.com>
---
 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 kobject *kobj,
 	return nvmem_bin_attr_get_umode(nvmem);
 }
 
+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 *kobj,
+				    struct bin_attribute *attr, char *buf,
+				    loff_t pos, size_t count)
+{
+	struct nvmem_cell_entry *entry;
+	struct nvmem_cell *cell = NULL;
+	size_t cell_sz, read_len;
+	void *content;
+
+	entry = attr->private;
+	cell = nvmem_create_cell(entry, entry->name, 0);
+	if (IS_ERR(cell))
+		return PTR_ERR(cell);
+
+	if (!cell)
+		return -EINVAL;
+
+	content = nvmem_cell_read(cell, &cell_sz);
+	if (IS_ERR(content)) {
+		read_len = PTR_ERR(content);
+		goto destroy_cell;
+	}
+
+	read_len = 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 = {
 	.attr	= {
@@ -351,11 +388,21 @@ static const struct attribute_group nvmem_bin_group = {
 	.is_bin_visible = nvmem_bin_attr_is_visible,
 };
 
+/* Cell attributes will be dynamically allocated */
+static struct attribute_group nvmem_cells_group = {
+	.name		= "cells",
+};
+
 static const struct attribute_group *nvmem_dev_groups[] = {
 	&nvmem_bin_group,
 	NULL,
 };
 
+static const struct attribute_group *nvmem_cells_groups[] = {
+	&nvmem_cells_group,
+	NULL,
+};
+
 static struct bin_attribute bin_attr_nvmem_eeprom_compat = {
 	.attr	= {
 		.name	= "eeprom",
@@ -411,6 +458,64 @@ static void nvmem_sysfs_remove_compat(struct nvmem_device *nvmem,
 		device_remove_bin_file(nvmem->base_dev, &nvmem->eeprom);
 }
 
+static int nvmem_populate_sysfs_cells(struct nvmem_device *nvmem)
+{
+	struct bin_attribute **cells_attrs, *attrs;
+	struct nvmem_cell_entry *entry;
+	unsigned int ncells = 0, i = 0;
+	int ret = 0;
+
+	mutex_lock(&nvmem_mutex);
+
+	if (list_empty(&nvmem->cells)) {
+		nvmem_cells_group.bin_attrs = NULL;
+		goto unlock_mutex;
+	}
+
+	/* Allocate an array of attributes with a sentinel */
+	ncells = list_count_nodes(&nvmem->cells);
+	cells_attrs = devm_kcalloc(&nvmem->dev, ncells + 1,
+				   sizeof(struct bin_attribute *), GFP_KERNEL);
+	if (!cells_attrs) {
+		ret = -ENOMEM;
+		goto unlock_mutex;
+	}
+
+	attrs = devm_kcalloc(&nvmem->dev, ncells, sizeof(struct bin_attribute), GFP_KERNEL);
+	if (!attrs) {
+		ret = -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 = devm_kasprintf(&nvmem->dev, GFP_KERNEL,
+						    "%s@%x", entry->name,
+						    entry->offset);
+		attrs[i].attr.mode = 0444;
+		attrs[i].size = entry->bytes;
+		attrs[i].read = &nvmem_cell_attr_read;
+		attrs[i].private = entry;
+		if (!attrs[i].attr.name) {
+			ret = -ENOMEM;
+			goto unlock_mutex;
+		}
+
+		cells_attrs[i] = &attrs[i];
+		i++;
+	}
+
+	nvmem_cells_group.bin_attrs = cells_attrs;
+
+	ret = devm_device_add_groups(&nvmem->dev, nvmem_cells_groups);
+
+unlock_mutex:
+	mutex_unlock(&nvmem_mutex);
+
+	return ret;
+}
+
 #else /* CONFIG_NVMEM_SYSFS */
 
 static int nvmem_sysfs_setup_compat(struct nvmem_device *nvmem,
@@ -2148,8 +2253,16 @@ static int nvmem_try_matching_available_layout(struct nvmem_device *nvmem)
 	if (ret)
 		goto put_layout;
 
+#ifdef CONFIG_NVMEM_SYSFS
+	ret = nvmem_populate_sysfs_cells(nvmem);
+	if (ret)
+		goto del_cells;
+#endif
+
 	return 0;
 
+del_cells:
+	nvmem_device_remove_all_cells(nvmem);
 put_layout:
 	nvmem_layout_put(nvmem->layout);
 	return ret;
-- 
2.34.1

Re: [PATCH v7 7/7] nvmem: core: Expose cells through sysfs

[kernel test robot]

Hi Miquel,

kernel test robot noticed the following build warnings:

[auto build test WARNING on char-misc/char-misc-testing]
[also build test WARNING on char-misc/char-misc-next char-misc/char-misc-linus linus/master v6.5-rc4 next-20230801]
[If your patch is applied to the wrong git tree, kindly drop us a note.
And when submitting patch, we suggest to use '--base' as documented in
https://git-scm.com/docs/git-format-patch#_base_tree_information]

url:    https://github.com/intel-lab-lkp/linux/commits/Miquel-Raynal/nvmem-core-Create-all-cells-before-adding-the-nvmem-device/20230802-022331
base:   char-misc/char-misc-testing
patch link:    https://lore.kernel.org/r/20230801182132.1058707-8-miquel.raynal%40bootlin.com
patch subject: [PATCH v7 7/7] nvmem: core: Expose cells through sysfs
config: x86_64-randconfig-x005-20230731 (https://download.01.org/0day-ci/archive/20230802/202308021505.FG8g7tZG-lkp@intel.com/config)
compiler: clang version 16.0.4 (https://github.com/llvm/llvm-project.git ae42196bc493ffe877a7e3dff8be32035dea4d07)
reproduce: (https://download.01.org/0day-ci/archive/20230802/202308021505.FG8g7tZG-lkp@intel.com/reproduce)

If you fix the issue in a separate patch/commit (i.e. not just a new version of
the same patch/commit), kindly add following tags
| Reported-by: kernel test robot <lkp@intel.com>
| Closes: https://lore.kernel.org/oe-kbuild-all/202308021505.FG8g7tZG-lkp@intel.com/

All warnings (new ones prefixed by >>):

>> drivers/nvmem/core.c:2264:1: warning: unused label 'del_cells' [-Wunused-label]
   del_cells:
   ^~~~~~~~~~
   1 warning generated.


vim +/del_cells +2264 drivers/nvmem/core.c

  2261	
  2262		return 0;
  2263	
> 2264	del_cells:
  2265		nvmem_device_remove_all_cells(nvmem);
  2266	put_layout:
  2267		nvmem_layout_put(nvmem->layout);
  2268		return ret;
  2269	}
  2270	

-- 
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Re: [PATCH v7 7/7] nvmem: core: Expose cells through sysfs

[Miquel Raynal]

Hello,

lkp@intel.com wrote on Wed, 2 Aug 2023 15:40:10 +0800:

> Hi Miquel,
> 
> kernel test robot noticed the following build warnings:
> 
> [auto build test WARNING on char-misc/char-misc-testing]
> [also build test WARNING on char-misc/char-misc-next char-misc/char-misc-linus linus/master v6.5-rc4 next-20230801]
> [If your patch is applied to the wrong git tree, kindly drop us a note.
> And when submitting patch, we suggest to use '--base' as documented in
> https://git-scm.com/docs/git-format-patch#_base_tree_information]
> 
> url:    https://github.com/intel-lab-lkp/linux/commits/Miquel-Raynal/nvmem-core-Create-all-cells-before-adding-the-nvmem-device/20230802-022331
> base:   char-misc/char-misc-testing
> patch link:    https://lore.kernel.org/r/20230801182132.1058707-8-miquel.raynal%40bootlin.com
> patch subject: [PATCH v7 7/7] nvmem: core: Expose cells through sysfs
> config: x86_64-randconfig-x005-20230731 (https://download.01.org/0day-ci/archive/20230802/202308021505.FG8g7tZG-lkp@intel.com/config)
> compiler: clang version 16.0.4 (https://github.com/llvm/llvm-project.git ae42196bc493ffe877a7e3dff8be32035dea4d07)
> reproduce: (https://download.01.org/0day-ci/archive/20230802/202308021505.FG8g7tZG-lkp@intel.com/reproduce)
> 
> If you fix the issue in a separate patch/commit (i.e. not just a new version of
> the same patch/commit), kindly add following tags
> | Reported-by: kernel test robot <lkp@intel.com>
> | Closes: https://lore.kernel.org/oe-kbuild-all/202308021505.FG8g7tZG-lkp@intel.com/
> 
> All warnings (new ones prefixed by >>):
> 
> >> drivers/nvmem/core.c:2264:1: warning: unused label 'del_cells' [-Wunused-label]  
>    del_cells:
>    ^~~~~~~~~~
>    1 warning generated.

This warning triggers with CONFIG_NVMEM_SYSFS=n, I'll fix that.
I'll wait a bit anyway to get some feedback about the new approach.

> 
> 
> vim +/del_cells +2264 drivers/nvmem/core.c
> 
>   2261	
>   2262		return 0;
>   2263	
> > 2264	del_cells:  
>   2265		nvmem_device_remove_all_cells(nvmem);
>   2266	put_layout:
>   2267		nvmem_layout_put(nvmem->layout);
>   2268		return ret;
>   2269	}
>   2270	
> 


Thanks,
Miquèl

Re: [PATCH v7 7/7] nvmem: core: Expose cells through sysfs

[kernel test robot]

Hi Miquel,

kernel test robot noticed the following build warnings:

[auto build test WARNING on char-misc/char-misc-testing]
[also build test WARNING on char-misc/char-misc-next char-misc/char-misc-linus linus/master v6.5-rc5 next-20230808]
[If your patch is applied to the wrong git tree, kindly drop us a note.
And when submitting patch, we suggest to use '--base' as documented in
https://git-scm.com/docs/git-format-patch#_base_tree_information]

url:    https://github.com/intel-lab-lkp/linux/commits/Miquel-Raynal/nvmem-core-Create-all-cells-before-adding-the-nvmem-device/20230802-022331
base:   char-misc/char-misc-testing
patch link:    https://lore.kernel.org/r/20230801182132.1058707-8-miquel.raynal%40bootlin.com
patch subject: [PATCH v7 7/7] nvmem: core: Expose cells through sysfs
config: x86_64-randconfig-x006-20230808 (https://download.01.org/0day-ci/archive/20230808/202308081956.p8FHCJY9-lkp@intel.com/config)
compiler: gcc-12 (Debian 12.2.0-14) 12.2.0
reproduce: (https://download.01.org/0day-ci/archive/20230808/202308081956.p8FHCJY9-lkp@intel.com/reproduce)

If you fix the issue in a separate patch/commit (i.e. not just a new version of
the same patch/commit), kindly add following tags
| Reported-by: kernel test robot <lkp@intel.com>
| Closes: https://lore.kernel.org/oe-kbuild-all/202308081956.p8FHCJY9-lkp@intel.com/

All warnings (new ones prefixed by >>):

   drivers/nvmem/core.c: In function 'nvmem_try_matching_available_layout':
>> drivers/nvmem/core.c:2264:1: warning: label 'del_cells' defined but not used [-Wunused-label]
    2264 | del_cells:
         | ^~~~~~~~~


vim +/del_cells +2264 drivers/nvmem/core.c

  2261	
  2262		return 0;
  2263	
> 2264	del_cells:
  2265		nvmem_device_remove_all_cells(nvmem);
  2266	put_layout:
  2267		nvmem_layout_put(nvmem->layout);
  2268		return ret;
  2269	}
  2270	

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