On Thu, Oct 5, 2023 at 6:22 AM Miquel Raynal <miquel.raynal@xxxxxxxxxxx> wrote: > > 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@77 > 00000000 54 57 |TW| > crc32@88 > 00000000 bb cd 51 98 |..Q.| > device-version@49 > 00000000 02 |.| > diag-version@80 > 00000000 56 31 2e 30 2e 30 |V1.0.0| > label-revision@4c > 00000000 44 31 |D1| > mac-address@2c > 00000000 18 be 92 13 9a 00 |......| > manufacture-date@34 > 00000000 30 32 2f 32 34 2f 32 30 32 31 20 31 38 3a 35 39 |02/24/2021 18:59| > manufacturer@72 > 00000000 44 4e 49 |DNI| > num-macs@6e > 00000000 00 40 |.@| > onie-version@61 > 00000000 32 30 32 30 2e 31 31 2d 56 30 31 |2020.11-V01| > platform-name@50 > 00000000 38 38 46 37 30 34 30 2f 38 38 46 36 38 32 30 |88F7040/88F6820| > product-name@d > 00000000 54 4e 34 38 4d 2d 50 2d 44 4e |TN48M-P-DN| > serial-number@19 > 00000000 54 4e 34 38 31 50 32 54 57 32 30 34 32 30 33 32 |TN481P2TW2042032| > vendor@7b > 00000000 44 4e 49 |DNI| > > Current support does not include: > * The knowledge of the type of data (binary vs. ASCII), so by default > all cells are exposed in binary form. > * Write support. > > Changes in v11: > * The nvmem layouts are now regular devices and not platform devices > anymore. They are registered into the nvmem-layout bus (so there is a > new /sysfs/bus/nvmem-layouts entry that gets created. All the code for > this new bus is located under drivers/nvmem/layouts.c and is part of > the main core. The core device-driver logic applies without too much > additional code besides the registration of the bus and a bit of > glue. I see no need for more detailed structures for now but this can > be improved later as needed. > > Changes in v10: > * All preparation patches have been picked-up by Srinivas. > * Rebased on top of v6.6-rc1. > * Fix an error path in the probe due to the recent additions. > > Changes in v9: > * Hopefully fixed the creation of sysfs entries when describing the > cells using the legacy layout, as reported by Chen-Yu. > * Dropped the nvmem-specific device list and used the driver core list > instead as advised by Greg. > > Changes in v8: > * Fix a compilation warning whith !CONFIG_NVMEM_SYSFS. > * Add a patch to return NULL when no layout is found (reported by Dan > Carpenter). > * Fixed the documentation as well as the cover letter regarding the > addition of addresses in the cell names. > > 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): > of: device: Export of_device_make_bus_id() > nvmem: Clarify the situation when there is no DT node available > nvmem: Move of_nvmem_layout_get_container() in another header > nvmem: Create a header for internal sharing > nvmem: core: Rework layouts to become regular devices > ABI: sysfs-nvmem-cells: Expose cells through sysfs > nvmem: core: Expose cells through sysfs Tested-by: Chen-Yu Tsai <wenst@xxxxxxxxxxxx> on a Juniper (MT8183) Chromebook. Note that this device uses the legacy layout format. > Documentation/ABI/testing/sysfs-nvmem-cells | 21 ++ > drivers/nvmem/Makefile | 2 +- > drivers/nvmem/core.c | 308 +++++++++++++++----- > drivers/nvmem/internals.h | 40 +++ > drivers/nvmem/layouts.c | 171 +++++++++++ > drivers/nvmem/layouts/onie-tlv.c | 37 ++- > drivers/nvmem/layouts/sl28vpd.c | 37 ++- > drivers/of/device.c | 41 +++ > drivers/of/platform.c | 40 --- > include/linux/nvmem-consumer.h | 7 - > include/linux/nvmem-provider.h | 38 ++- > include/linux/of_device.h | 6 + > 12 files changed, 614 insertions(+), 134 deletions(-) > create mode 100644 Documentation/ABI/testing/sysfs-nvmem-cells > create mode 100644 drivers/nvmem/internals.h > create mode 100644 drivers/nvmem/layouts.c > > -- > 2.34.1 >
