diff mbox series

[1/2] ABI: sysfs-nvmem-cells: Expose cells through sysfs

Message ID 20230523100239.307574-2-miquel.raynal@bootlin.com
State New
Headers
Series NVMEM cells in sysfs |

Commit Message

Miquel Raynal May 23, 2023, 10:02 a.m. UTC 
  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>
---
 Documentation/ABI/testing/sysfs-nvmem-cells | 21 +++++++++++++++++++++
 1 file changed, 21 insertions(+)
 create mode 100644 Documentation/ABI/testing/sysfs-nvmem-cells

Comments

Greg KH May 23, 2023, 4:59 p.m. UTC | #1 
On Tue, May 23, 2023 at 12:02:38PM +0200, Miquel Raynal wrote:
> +		The cells/ folder contains one file per cell exposed by
> +		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).
> +		There is currently no write permission but this could
> +		evolve in the future if the need arises.

No need to have these 2 lines, you don't know what will happen in the
future, don't tease people :)

thanks,

greg k-h
Miquel Raynal May 23, 2023, 5:14 p.m. UTC | #2 
Hi Greg,

gregkh@linuxfoundation.org wrote on Tue, 23 May 2023 17:59:40 +0100:

> On Tue, May 23, 2023 at 12:02:38PM +0200, Miquel Raynal wrote:
> > +		The cells/ folder contains one file per cell exposed by
> > +		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).
> > +		There is currently no write permission but this could
> > +		evolve in the future if the need arises.  
> 
> No need to have these 2 lines, you don't know what will happen in the
> future, don't tease people :)

Sure!

Thanks,
Miquèl
diff mbox series

Patch

diff --git a/Documentation/ABI/testing/sysfs-nvmem-cells b/Documentation/ABI/testing/sysfs-nvmem-cells
new file mode 100644
index 000000000000..d0247bead8a1
--- /dev/null
+++ b/Documentation/ABI/testing/sysfs-nvmem-cells
@@ -0,0 +1,21 @@ 
+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.
+		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).
+		There is currently no write permission but this could
+		evolve in the future if the need arises.
+		Note: This file is only present if CONFIG_NVMEM_SYSFS
+		is enabled
+
+		ex::
+
+		  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