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Date:   Tue, 27 Jul 2021 18:13:26 +0200
From:   Martin Kaiser <martin@kaiser.cx>
To:     Manivannan Sadhasivam <manivannan.sadhasivam@linaro.org>
Cc:     miquel.raynal@bootlin.com, richard@nod.at, vigneshr@ti.com,
        boris.brezillon@collabora.com, tudor.ambarus@microchip.com,
        linux-mtd@lists.infradead.org, linux-kernel@vger.kernel.org,
        dan.carpenter@oracle.com
Subject: Re: [PATCH] mtd: rawnand: Fix probe failure due to
 of_get_nand_secure_regions()
Message-ID: <20210727161326.wozj23a3sblibwpk@viti.kaiser.cx>
References: <20210727062813.32619-1-manivannan.sadhasivam@linaro.org>
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Sender: Martin Kaiser <martin@viti.kaiser.cx>
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Hi Mani and all,

Thus wrote Manivannan Sadhasivam (manivannan.sadhasivam@linaro.org):

> Due to 14f97f0b8e2b, the rawnand platforms without "secure-regions"
> property defined in DT fails to probe. The issue is,
> of_get_nand_secure_regions() errors out if
> of_property_count_elems_of_size() returns a negative error code.

> If the "secure-regions" property is not present in DT, then also we'll
> get -EINVAL from of_property_count_elems_of_size() but it should not
> be treated as an error for platforms not declaring "secure-regions"
> in DT.

> So fix this behaviour by checking for the existence of that property in
> DT and return 0 if it is not present.

> Fixes: 14f97f0b8e2b ("mtd: rawnand: Add a check in of_get_nand_secure_regions()")
> Reported-by: Martin Kaiser <martin@kaiser.cx>
> Signed-off-by: Manivannan Sadhasivam <manivannan.sadhasivam@linaro.org>
> ---
>  drivers/mtd/nand/raw/nand_base.c | 6 ++++++
>  1 file changed, 6 insertions(+)

> diff --git a/drivers/mtd/nand/raw/nand_base.c b/drivers/mtd/nand/raw/nand_base.c
> index cbba46432e39..3d6c6e880520 100644
> --- a/drivers/mtd/nand/raw/nand_base.c
> +++ b/drivers/mtd/nand/raw/nand_base.c
> @@ -5228,8 +5228,14 @@ static bool of_get_nand_on_flash_bbt(struct device_node *np)
>  static int of_get_nand_secure_regions(struct nand_chip *chip)
>  {
>  	struct device_node *dn = nand_get_flash_node(chip);
> +	struct property *prop;
>  	int nr_elem, i, j;

> +	/* Only proceed if the "secure-regions" property is present in DT */
> +	prop = of_find_property(dn, "secure-regions", NULL);
> +	if (!prop)
> +		return 0;
> +
>  	nr_elem = of_property_count_elems_of_size(dn, "secure-regions", sizeof(u64));
>  	if (nr_elem <= 0)
>  		return nr_elem;
> -- 
> 2.25.1

not surprisingly, this fixes the issue for me.

Reviewed-by: Martin Kaiser <martin@kaiser.cx>
Tested-by: Martin Kaiser <martin@kaiser.cx>

Still, I was wondering if the behaviour of of_property_count_elems_of_size
makes sense. Without a prior check, there's no chance for the caller to
distinguish between "property is absent" and "property is malformed". 

Thanks,
Martin