linux-kernel - Re: [PATCH v2 1/3] nvmem: core: introduce cells parser

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Date:   Mon, 21 Jun 2021 12:00:10 +0100
From:   Srinivas Kandagatla <srinivas.kandagatla@...aro.org>
To:     Vadym Kochan <vadym.kochan@...ision.eu>
Cc:     Rob Herring <robh+dt@...nel.org>, linux-kernel@...r.kernel.org,
        devicetree@...r.kernel.org, Robert Marko <robert.marko@...tura.hr>
Subject: Re: [PATCH v2 1/3] nvmem: core: introduce cells parser



On 16/06/2021 13:33, Vadym Kochan wrote:
>>> diff --git a/drivers/nvmem/core.c b/drivers/nvmem/core.c
>>> index bca671ff4e54..648373ced6d4 100644
>>> --- a/drivers/nvmem/core.c
>>> +++ b/drivers/nvmem/core.c
>>> @@ -39,6 +39,7 @@ struct nvmem_device {
>>>    	nvmem_reg_read_t	reg_read;
>>>    	nvmem_reg_write_t	reg_write;
>>>    	struct gpio_desc	*wp_gpio;
>>> +	struct nvmem_parser_data *parser_data;
>> This should be renamed to nvmem_cell_info_parser or something on those lines
>> to avoid any misunderstanding on what exactly this parser is about.
>>
>> May be can totally avoid this by using parser name only during register.
>>
> I added this to keep parsed cells particulary for this nvmem in case
> same parser is used for several nvmem's and mostly because of using also
> cell lookup info. I will try to also answer your below question why do I need
> lookups ?
> 
> I use of_get_mac_address() func to fetch mac-address from nvmem cell.
> Eventually this func calls of_get_mac_addr_nvmem() which (as I understand it
> correctly) can find cells via DT by parsing "nvmem-cell-names" or via cell lookup
> info of platform_device. I use the 2nd option with the following sample
> solution:
> 
> 	## DT ##
> 	eeprom_at24: at24@56 {
> 		compatible = "atmel,24c32";
> 		nvmem-cell-parser-name = "onie-tlv-cells";
> 		reg = <0x56>;
> 	};
> 
> 	onie_tlv_parser: onie-tlv-cells {
> 		compatible = "nvmem-cell-parser";
> 		status = "okay";
> 
> ---> add ability here to map cell con_id to cell_name ?
> 
> 	};
> 
> 	some_dev_node {
> 		compatible = "xxx";
> 		base-mac-provider = <&onie_tlv_parser>;

Real nvmem provider is eeprom_at24, why do you use onie_tlv_parse as 
your mac provider?
If you use eeprom_at24 then of_get_mac_address() should get mac-address 
directly from cell info.


> 		status = "okay";
> 	};
> 	########
> 
> 	== CODE ==
> 	base_mac_np = of_parse_phandle(np, "base-mac-provider", 0);
> 	ret = of_get_mac_address(base_mac_np, base_mac);
> 	==========
> 
> 
> And it works with this implementation because onie-tlv-cells is
> registered as platform_device which name is the same as parser's name.
> So the really tricky part for me is to make this cells lookup work.

cell lookups are more of intended for board files, adding them in this 
case is really not correct.  The whole purpose of this driver is to 
parse the tlv cell infos into nvmem cell info.


--srini


> 
> Of course would be great if you can point a way/idea to get rid the need of
> lookups.
>