[v8,0/8] NVMEM cells in sysfs

  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.

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 (8):
  nvmem: core: Create all cells before adding the nvmem device
  nvmem: core: Return NULL when no nvmem layout is found
  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              |   4 +-
 include/linux/nvmem-provider.h              |  11 +-
 6 files changed, 329 insertions(+), 54 deletions(-)
 create mode 100644 Documentation/ABI/testing/sysfs-nvmem-cells
  

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?

ChenYu

> 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 (8):
>   nvmem: core: Create all cells before adding the nvmem device
>   nvmem: core: Return NULL when no nvmem layout is found
>   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              |   4 +-
>  include/linux/nvmem-provider.h              |  11 +-
>  6 files changed, 329 insertions(+), 54 deletions(-)
>  create mode 100644 Documentation/ABI/testing/sysfs-nvmem-cells
>
> --
> 2.34.1
>
  

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.

Thanks for the feedback!
Miquèl
  

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.

Thanks a lot for testing!
Miquèl
  

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.
  

Hi Chen-Yu,

wenst@chromium.org wrote on Tue, 8 Aug 2023 10:56:36 +0800:

> 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.

No problem ;) Thanks a lot for the testing, it's highly appreciated.

Miquèl