linux-kernel - Re: [PATCH v2] nvmem: core: don't consider subnodes not matching binding

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Date:   Mon, 6 Apr 2020 13:33:43 +0100
From:   Srinivas Kandagatla <srinivas.kandagatla@...aro.org>
To:     Ahmad Fatoum <a.fatoum@...gutronix.de>
Cc:     kernel@...gutronix.de, Christian Eggers <CEggers@...i.de>,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2] nvmem: core: don't consider subnodes not matching
 binding



On 23/03/2020 15:28, Ahmad Fatoum wrote:
> The nvmem cell binding applies to objects which match "^.*@[0-9a-f]+$",
> but so far the driver has matched all objects and failed if they didn't
> have the expected properties.
> 
> The driver's behavior in this regard precludes future extension of
> EEPROMs by child nodes other than nvmem and clashes with the barebox
> bootloader binding that extends the fixed-partitions MTD binding to
> EEPROMs as it tries to interpret the "fixed-partitions"-compatible
> partitions node as a nvmem cell.
> 
> Solve this issue by skipping all subnodes that don't contain an @.
> 
> This still allows for cell names like `partitions@0,0', but this
NACK.. thats nasty hack!
Its standard practice as per device tree specs to have nodes name as 
"node-name@...t-address"

Ref: 
https://github.com/devicetree-org/devicetree-specification/releases/download/v0.3/devicetree-specification-v0.3.pdf


> is much less likely to cause future collisions.

There have been discussions on this topic in the past at:

https://patchwork.ozlabs.org/patch/890741/

We need to come up with a better solution!

--srini

> 
> Signed-off-by: Ahmad Fatoum <a.fatoum@...gutronix.de>
> ---
> v1 -> v2:
>    use ->full_name instead of ->name as to not break existing correct
>    cells (Christian)
> ---
>   drivers/nvmem/core.c | 2 ++
>   1 file changed, 2 insertions(+)
> 
> diff --git a/drivers/nvmem/core.c b/drivers/nvmem/core.c
> index ef326f243f36..f051051fb1a8 100644
> --- a/drivers/nvmem/core.c
> +++ b/drivers/nvmem/core.c
> @@ -278,6 +278,8 @@ static int nvmem_add_cells_from_of(struct nvmem_device *nvmem)
>   	parent = dev->of_node;
>   
>   	for_each_child_of_node(parent, child) {
> +		if (!strchr(kbasename(child->full_name), '@'))
> +			continue;
>   		addr = of_get_property(child, "reg", &len);
>   		if (!addr || (len < 2 * sizeof(u32))) {
>   			dev_err(dev, "nvmem: invalid reg on %pOF\n", child);
>