From: "Rafał Miłecki" <zajec5@gmail.com>
To: Michael Walle <michael@walle.cc>,
linux-mtd@lists.infradead.org, devicetree@vger.kernel.org,
linux-kernel@vger.kernel.org,
linux-arm-kernel@lists.infradead.org, netdev@vger.kernel.org
Cc: Miquel Raynal <miquel.raynal@bootlin.com>,
Richard Weinberger <richard@nod.at>,
Vignesh Raghavendra <vigneshr@ti.com>,
Rob Herring <robh+dt@kernel.org>,
Srinivas Kandagatla <srinivas.kandagatla@linaro.org>,
Shawn Guo <shawnguo@kernel.org>, Li Yang <leoyang.li@nxp.com>,
Frank Rowand <frowand.list@gmail.com>,
"David S . Miller" <davem@davemloft.net>,
Jakub Kicinski <kuba@kernel.org>,
Ansuel Smith <ansuelsmth@gmail.com>, Andrew Lunn <andrew@lunn.ch>
Subject: Re: [PATCH 6/8] nvmem: transformations: ethernet address offset support
Date: Tue, 25 Jan 2022 13:08:58 +0100 [thread overview]
Message-ID: <455f4360-34fe-7fee-66d5-fd945fe1e086@gmail.com> (raw)
In-Reply-To: <20211228142549.1275412-7-michael@walle.cc>
On 28.12.2021 15:25, Michael Walle wrote:
> An nvmem cell might just contain a base MAC address. To generate a
> address of a specific interface, add a transformation to add an offset
> to this base address.
>
> Add a generic implementation and the first user of it, namely the sl28
> vpd storage.
>
> Signed-off-by: Michael Walle <michael@walle.cc>
> ---
> drivers/nvmem/transformations.c | 45 +++++++++++++++++++++++++++++++++
> 1 file changed, 45 insertions(+)
>
> diff --git a/drivers/nvmem/transformations.c b/drivers/nvmem/transformations.c
> index 61642a9feefb..15cd26da1f83 100644
> --- a/drivers/nvmem/transformations.c
> +++ b/drivers/nvmem/transformations.c
> @@ -12,7 +12,52 @@ struct nvmem_transformations {
> nvmem_cell_post_process_t pp;
> };
>
> +/**
> + * nvmem_transform_mac_address_offset() - Add an offset to a mac address cell
> + *
> + * A simple transformation which treats the index argument as an offset and add
> + * it to a mac address. This is useful, if the nvmem cell stores a base
> + * ethernet address.
> + *
> + * @index: nvmem cell index
> + * @data: nvmem data
> + * @bytes: length of the data
> + *
> + * Return: 0 or negative error code on failure.
> + */
> +static int nvmem_transform_mac_address_offset(int index, unsigned int offset,
> + void *data, size_t bytes)
> +{
> + if (bytes != ETH_ALEN)
> + return -EINVAL;
> +
> + if (index < 0)
> + return -EINVAL;
> +
> + if (!is_valid_ether_addr(data))
> + return -EINVAL;
> +
> + eth_addr_add(data, index);
> +
> + return 0;
> +}
> +
> +static int nvmem_kontron_sl28_vpd_pp(void *priv, const char *id, int index,
> + unsigned int offset, void *data,
> + size_t bytes)
> +{
> + if (!id)
> + return 0;
> +
> + if (!strcmp(id, "mac-address"))
> + return nvmem_transform_mac_address_offset(index, offset, data,
> + bytes);
> +
> + return 0;
> +}
> +
> static const struct nvmem_transformations nvmem_transformations[] = {
> + { .compatible = "kontron,sl28-vpd", .pp = nvmem_kontron_sl28_vpd_pp },
> {}
> };
I think it's a rather bad solution that won't scale well at all.
You'll end up with a lot of NVMEM device specific strings and code in a
NVMEM core.
You'll have a lot of duplicated code (many device specific functions
calling e.g. nvmem_transform_mac_address_offset()).
I think it also ignores fact that one NVMEM device can be reused in
multiple platforms / device models using different (e.g. vendor / device
specific) cells.
What if we have:
1. Foo company using "kontron,sl28-vpd" with NVMEM cells:
a. "mac-address"
b. "mac-address-2"
c. "mac-address-3"
2. Bar company using "kontron,sl28-vpd" with NVMEM cell:
a. "mac-address"
In the first case you don't want any transformation.
If you consider using transformations for ASCII formats too then it
causes another conflict issue. Consider two devices:
1. Foo company device with BIN format of MAC
2. Bar company device with ASCII format of MAC
Both may use exactly the same binding:
partition@0 {
compatible = "nvmem-cells";
reg = <0x0 0x100000>;
label = "bootloader";
#address-cells = <1>;
#size-cells = <1>;
mac-address@100 {
reg = <0x100 0x6>;
};
};
how are you going to handle them with proposed implementation? You can't
support both if you share "nvmem-cells" compatible string.
I think that what can solve those problems is assing "compatible" to
NVMEM cells.
Let me think about details of that possible solution.
next prev parent reply other threads:[~2022-01-25 12:14 UTC|newest]
Thread overview: 18+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-12-28 14:25 [PATCH 0/8] nvmem: add ethernet address offset support Michael Walle
2021-12-28 14:25 ` [PATCH 1/8] of: base: add of_parse_phandle_with_optional_args() Michael Walle
2022-01-10 19:06 ` Rob Herring
2021-12-28 14:25 ` [PATCH 2/8] dt-bindings: nvmem: add transformation bindings Michael Walle
2021-12-29 17:34 ` Rob Herring
2022-01-04 15:03 ` Rob Herring
2022-01-05 8:25 ` Michael Walle
2022-01-05 14:20 ` Rob Herring
2021-12-28 14:25 ` [PATCH 3/8] nvmem: core: add an index parameter to the cell Michael Walle
2021-12-28 14:25 ` [PATCH 4/8] nvmem: core: add transformations support Michael Walle
2021-12-28 14:25 ` [PATCH 5/8] net: add helper eth_addr_add() Michael Walle
2022-01-25 10:24 ` Rafał Miłecki
2022-08-25 9:46 ` Michael Walle
2021-12-28 14:25 ` [PATCH 6/8] nvmem: transformations: ethernet address offset support Michael Walle
2022-01-25 12:08 ` Rafał Miłecki [this message]
2022-01-25 14:59 ` Michael Walle
2021-12-28 14:25 ` [PATCH 7/8] arm64: dts: ls1028a: sl28: get MAC addresses from VPD Michael Walle
2021-12-28 14:25 ` [PATCH 8/8] arm64: defconfig: enable NVMEM transformations Michael Walle
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