linux-kernel - Re: [PATCH RESEND v5 1/3] ABI: sysfs-nvmem-cells: Expose cells through sysfs

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Date:   Sun, 16 Jul 2023 15:59:42 +0200
From:   Miquel Raynal <miquel.raynal@...tlin.com>
To:     Randy Dunlap <rdunlap@...radead.org>
Cc:     Srinivas Kandagatla <srinivas.kandagatla@...aro.org>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        linux-kernel@...r.kernel.org,
        Thomas Petazzoni <thomas.petazzoni@...tlin.com>,
        Robert Marko <robert.marko@...tura.hr>,
        Luka Perkov <luka.perkov@...tura.hr>
Subject: Re: [PATCH RESEND v5 1/3] ABI: sysfs-nvmem-cells: Expose cells
 through sysfs

Hi Randy,

rdunlap@...radead.org wrote on Thu, 13 Jul 2023 08:56:48 -0700:

> Hi,
> 
> On 7/13/23 00:55, 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@...tlin.com>
> > Reviewed-by: Greg Kroah-Hartman <gregkh@...uxfoundation.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..641a7d7dad76
> > --- /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@...tlin.com>
> > +Description:
> > +		The cells/ folder contains one file per cell exposed by  
> 
> (My shell doesn't show "folders". ;)

What do you mean? Is it your shell that needs fixing? Or is it
something that I need to fix?

> > +		the nvmem device. The name of the file is the cell name.
> > +		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  
> 
> add ending '.':    enabled.
> 
> > +
> > +		ex::  
> 
> 		Example::

Yup, I'll fix it in v6.

> or
> 		E.g.::
> 
> > +
> > +		  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  
> 


Thanks,
Miquèl