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Date: Tue, 6 Feb 2024 22:07:59 +0000
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Subject: Re: [PATCH 1/4] nvmem: core: Read into buffers larger than data
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To: Markus Schneider-Pargmann <msp@baylibre.com>, Nishanth Menon <nm@ti.com>,
 Vignesh Raghavendra <vigneshr@ti.com>, Tero Kristo <kristo@kernel.org>,
 Rob Herring <robh+dt@kernel.org>,
 Krzysztof Kozlowski <krzysztof.kozlowski+dt@linaro.org>,
 Conor Dooley <conor+dt@kernel.org>, Santosh Shilimkar <ssantosh@kernel.org>
Cc: Andrew Davis <afd@ti.com>, linux-arm-kernel@lists.infradead.org,
 devicetree@vger.kernel.org, linux-kernel@vger.kernel.org
References: <20240206143711.2410135-1-msp@baylibre.com>
 <20240206143711.2410135-2-msp@baylibre.com>
From: Srinivas Kandagatla <srinivas.kandagatla@linaro.org>
In-Reply-To: <20240206143711.2410135-2-msp@baylibre.com>
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On 06/02/2024 14:37, Markus Schneider-Pargmann wrote:
> The actual size that nvmem is using internally on a specific platform
> with a specific devicetree may not be known in the consumer code. The
> maximum size may be available at the same time.
> 
> Allow the use of larger buffers in nvmem_cell_read_common() by setting
> buffers that are too large to zero before copying into them.
> 
Can you explain why can we not use nvmem_cell_read() ?


there is an other thread to add get_size
https://www.spinics.net/lists/kernel/msg5075254.html

> Signed-off-by: Markus Schneider-Pargmann <msp@baylibre.com>
> ---
>   drivers/nvmem/core.c | 6 ++++--
>   1 file changed, 4 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/nvmem/core.c b/drivers/nvmem/core.c
> index 980123fb4dde..6fa061ede605 100644
> --- a/drivers/nvmem/core.c
> +++ b/drivers/nvmem/core.c
> @@ -1806,12 +1806,14 @@ static int nvmem_cell_read_common(struct device *dev, const char *cell_id,
>   		nvmem_cell_put(cell);
>   		return PTR_ERR(buf);
>   	}
> -	if (len != count) {
> +	if (len > count) {
>   		kfree(buf);
>   		nvmem_cell_put(cell);
>   		return -EINVAL;
> +	} else if (len < count) {
> +		memset(val + len, 0, count - len);
no please.. this really does not belong here.

--srini
>   	}
> -	memcpy(val, buf, count);
> +	memcpy(val, buf, len);
>   	kfree(buf);
>   	nvmem_cell_put(cell);
>