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    SubjectRe: [PATCH v8 0/8] NVMEM cells in sysfs
    On Mon, Aug 7, 2023 at 10:28 PM Miquel Raynal <miquel.raynal@bootlin.com> wrote:
    >
    > Hi Chen-Yu,
    >
    > miquel.raynal@bootlin.com wrote on Mon, 7 Aug 2023 11:20:40 +0200:
    >
    > > Hi Chen-Yu,
    > >
    > > wenst@chromium.org wrote on Mon, 7 Aug 2023 16:57:03 +0800:
    > >
    > > > On Mon, Aug 7, 2023 at 4:24 PM Miquel Raynal <miquel.raynal@bootlin.com> 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|
    > > > >
    > > > > 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.
    > > > >
    > > > > 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 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.
    > > >
    > > > It seems this version no longer creates cells for legacy DT layout formats?
    > > > So while I assume the issue I ran into is fixed, I don't see any cells
    > > > created on the MT8183 either.
    > > >
    > > > Is this intended?
    > >
    > > Not at all, but I am surprised they are no longer created. I will add
    > > fake cells and see how it behaves.
    >
    > Alright, I've got confused, the cells are still created, but in the
    > 'legacy' case, they no longer appear in sysfs. I guess that's what you
    > meant. I will move the sysfs creation to a better place indeed.

    That's right, the cells in sysfs aren't created. Sorry for the confusion.

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