Re: [PATCH v2 02/29] Documentation: nvmem: document lookup entries

2018-08-31 22:30 GMT+02:00 Brian Norris [off-list ref]:

On Fri, Aug 10, 2018 at 10:04:59AM +0200, Bartosz Golaszewski wrote:

quoted

From: Bartosz Golaszewski <redacted>

Describe the usage of nvmem cell lookup tables.

Signed-off-by: Bartosz Golaszewski <redacted>
---
 Documentation/nvmem/nvmem.txt | 28 ++++++++++++++++++++++++++++
 1 file changed, 28 insertions(+)

diff --git a/Documentation/nvmem/nvmem.txt b/Documentation/nvmem/nvmem.txt
index 8d8d8f58f96f..9d5e3ca2b4f3 100644
--- a/Documentation/nvmem/nvmem.txt
+++ b/Documentation/nvmem/nvmem.txt

@@ -58,6 +58,34 @@ static int qfprom_probe(struct platform_device *pdev)
 It is mandatory that the NVMEM provider has a regmap associated with its
 struct device. Failure to do would return error code from nvmem_register().

+Additionally it is possible to create nvmem cell lookup entries and register
+them with the nvmem framework from machine code as shown in the example below:

Maybe it's partially a lacking in the existing documentation, but what
does the "name" and the "nvmem_name" mean here? AFAICT, "nvmem_name" is
akin to a provider identifier; and "name" is a key to match with the
consumer. It feels like this should be in either the header / kerneldoc
or this file. Or maybe both.

Does this mean there can only be a single "mac-address" cell in the
system? I have systems where there are multiple MACs provided in flash
storage, and we need to map them to ethernet0 and ethernet1. Is that
supported here?

This is a shortcoming of the nvmem subsystem we discussed under
another patch in this series with Boris and Srinivas. I will try to
post a series addressing this next week. Basically there's a global
list of nvmem cells referenced only by name and unless you're using DT
you can only have a single cell with given name. I will address it by
introducing the standard dev_id/con_id resource association.

Bart

Brian

quoted

+static struct nvmem_cell_lookup foobar_lookup = {
+     .info = {
+             .name = "mac-address",
+             .offset = 0xd000,
+             .bytes = ERH_ALEN,
+     },
+     .nvmem_name = "foobar",
+};
+
+static void foobar_register(void)
+{
+     ...
+     nvmem_add_lookup_table(&foobar_lookup, 1);
+     ...
+}
+
+A lookup entry table can be later removed if needed:
+
+static void foobar_fini(void)
+{
+     ...
+     nvmem_del_lookup_table(&foobar_lookup, 1);
+     ...
+}
+
 NVMEM Consumers
 +++++++++++++++

--
2.18.0