On Thu, 14 Oct 2021 11:30:13 +0100 Srinivas Kandagatla srinivas.kandagatla@linaro.org wrote:
On 14/10/2021 11:06, Marek Behún wrote:
On Thu, 14 Oct 2021 09:26:27 +0100 Srinivas Kandagatla srinivas.kandagatla@linaro.org wrote:
On 14/10/2021 00:20, Marek Behún wrote:
Add device tree bindings for U-Boot environment NVMEM provider.
U-Boot environment can be stored at a specific offset of a MTD device, EEPROM, MMC, NAND or SATA device, on an UBI volume, or in a file on a filesystem.
The environment can contain information such as device's MAC address, which should be used by the ethernet controller node.
Have you looked at ./Documentation/devicetree/bindings/mtd/partitions/nvmem-cells.yaml ?
Hello srini,
yes, I have. What about it? :)
That binding won't work for u-boot-env, because the data are stored in a different way. A cell does not have a constant predetermined offset on the MTD.
Can't you dynamically update the nodes before nvmem-provider is registered?
Are you talking about dynamically updating nvmem-cell OF nodes, adding reg properties with actual offsets and lengths found after parsing?
The variables are stored as a sequence of values of format "name=value", separated by '\0's, for example: board=turris_mox\0ethaddr=00:11:22:33:44:55\0bootcmd=run distro_bootcmd\0.... Chaning lengths of values of variables, or deleting variables, moves the data around. Integers and MAC addresses are stored as strings, and so on.
Do you already have a provider driver for handing this.
Not yet, I will send the proposal together with a driver in next round.
How is pre parsing cell info and post processing data planned to be handled?
My plan was to read the variables from the u-boot-env partition, create a nvmem-cell for each variable, and then pair the ones mentioned in device tree with their DT nodes, and post-process according to type (post-processing would be done only for those mentioned in device tree, others would be left as strings).
Currently in nvmem core we do check for "reg" property for each cell, unless the provider driver is adding/updating dt entries dynamically before registering nvmem provider
I don't think updaring DT entries dynamically is a correct solution at all. Is this done in Linux? Updating device properties is something different, but changing DT properties seems wrong to me.
It will not work as it is. Alteast this is what I suggested in similar case where cell information is in tlv format.
Hmm. OK, I shall try to implement a driver for this and then will return to you.
Secondly mac-address seems to be delimited, we recently introduced post processing callback for provider driver [1], which should help in this case.
Cool, I shall use that.
If the nvmem-cell names are standard like "mac-address" then you do not need to add a new "type" binding to cell too, you can do post-processing based on name.
I plan to add functions of_nvmem_get_mac_address() nvmem_get_mac_address() which would look at (in this order): mac-address, address, mac-address-backup We have to keep the name "address" for backwards compatibility with one driver that uses this (drivers/net/ethernet/ni/nixge.c)
Thanks.
Marek