Re: [PATCH v3 01/10] of_net: add NVMEM support to of_get_mac_address

From: Sergei Shtylyov
Date: Fri May 03 2019 - 04:45:36 EST


On 03.05.2019 10:55, Petr Åtetiar wrote:

Many embedded devices have information such as MAC addresses stored
inside NVMEMs like EEPROMs and so on. Currently there are only two
drivers in the tree which benefit from NVMEM bindings.

Adding support for NVMEM into every other driver would mean adding a lot
of repetitive code. This patch allows us to configure MAC addresses in
various devices like ethernet and wireless adapters directly from
of_get_mac_address, which is already used by almost every driver in the

Predecessor of this patch which used directly MTD layer has originated
in OpenWrt some time ago and supports already about 497 use cases in 357
device tree files.

Cc: Alban Bedel <albeu@xxxxxxx>
Signed-off-by: Felix Fietkau <nbd@xxxxxxxx>
Signed-off-by: John Crispin <john@xxxxxxxxxxx>
Signed-off-by: Petr Åtetiar <ynezz@xxxxxxx>

Changes since v1:

* moved handling of nvmem after mac-address and local-mac-address properties

Changes since v2:

* moved of_get_mac_addr_nvmem after of_get_mac_addr(np, "address") call
* replaced kzalloc, kmemdup and kfree with it's devm variants
* introduced of_has_nvmem_mac_addr helper which checks if DT node has nvmem
cell with `mac-address`
* of_get_mac_address now returns ERR_PTR encoded error value

drivers/of/of_net.c | 65 ++++++++++++++++++++++++++++++++++++++++++++++++++---
1 file changed, 62 insertions(+), 3 deletions(-)

diff --git a/drivers/of/of_net.c b/drivers/of/of_net.c
index d820f3e..258ceb8 100644
--- a/drivers/of/of_net.c
+++ b/drivers/of/of_net.c
@@ -64,6 +113,9 @@ static const void *of_get_mac_addr(struct device_node *np, const char *name)
* addresses. Some older U-Boots only initialized 'local-mac-address'. In
* this case, the real MAC is in 'local-mac-address', and 'mac-address' exists
* but is all zeros.
+ *
+ * Return: Will be a valid pointer on success, NULL in case there wasn't
+ * 'mac-address' nvmem cell node found, and ERR_PTR in case of error.

Returning both NULL and error codes on failure is usually a sign of a misdesigned API. Why not always return an error code?


MBR, Sergei