Messages in this thread | | | Date | Sun, 23 Jul 2023 19:39:50 +0000 | From | "John Thomson" <> | Subject | Re: [PATCH v6 1/3] ABI: sysfs-nvmem-cells: Expose cells through sysfs |
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Hi Miquel,
On Mon, 17 Jul 2023, at 07:51, Miquel Raynal wrote: > 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 their position/size in the underlying device, but > these information were not accessible to the user. > > By exposing the nvmem cells to the user through a dedicated cell/ folder > containing one file per cell, we provide a straightforward access to > useful user information without the need for re-writing a userland > parser. Content of nvmem cells is usually: product names, manufacturing > date, MAC addresses, etc, > > Signed-off-by: Miquel Raynal <miquel.raynal@bootlin.com> > Reviewed-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> > --- > Documentation/ABI/testing/sysfs-nvmem-cells | 19 +++++++++++++++++++ > 1 file changed, 19 insertions(+) > create mode 100644 Documentation/ABI/testing/sysfs-nvmem-cells > > diff --git a/Documentation/ABI/testing/sysfs-nvmem-cells > b/Documentation/ABI/testing/sysfs-nvmem-cells > new file mode 100644 > index 000000000000..b2d15a8d36e5 > --- /dev/null > +++ b/Documentation/ABI/testing/sysfs-nvmem-cells > @@ -0,0 +1,19 @@ > +What: /sys/bus/nvmem/devices/.../cells/<cell-name> > +Date: May 2023 > +KernelVersion: 6.5 > +Contact: Miquel Raynal <miquel.raynal@bootlin.com> > +Description: > + The "cells" folder contains one file per cell exposed by > + the nvmem device. The name of the file is the cell name.
Could we consider using a file within a folder (name defined by cell propertys) to access the cell bytes? Example (pick the best path and filename): /sys/bus/nvmem/devices/.../cells/<cell-name>/bytes
That way, it is much easier to expand this at a later stage, like adding an of_node link at /sys/bus/nvmem/devices/.../cells/<cell-name>/of_node or exposing other nvmem cell properties.
This is particularly relevant given the cell-name alone does not always uniquely represent a cell on an nvmem device. https://lore.kernel.org/lkml/ZLaZ7fzUSsa0Igx1@makrotopia.org/ https://lore.kernel.org/lkml/e7173ab2-d3b2-4f75-beb8-32593b868774@www.fastmail.com/
> + The length of the file is the size of the cell (when > + known). The content of the file is the binary content of > + the cell (may sometimes be ASCII, likely without > + trailing character). > + Note: This file is only present if CONFIG_NVMEM_SYSFS > + is enabled. > + > + Example:: > + > + hexdump -C /sys/bus/nvmem/devices/1-00563/cells/product-name > + 00000000 54 4e 34 38 4d 2d 50 2d 44 4e |TN48M-P-DN| > + 0000000a > -- > 2.34.1
Cheers,
-- John Thomson
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