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

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Message-ID: <153c8781-a83a-d7d9-92b2-b82ca9ab06aa@infradead.org>
Date:   Thu, 13 Jul 2023 08:56:48 -0700
From:   Randy Dunlap <rdunlap@...radead.org>
To:     Miquel Raynal <miquel.raynal@...tlin.com>,
        Srinivas Kandagatla <srinivas.kandagatla@...aro.org>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        linux-kernel@...r.kernel.org
Cc:     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,

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". ;)

> +		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::
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

-- 
~Randy