linux-kernel - Re: [PATCH 4/4] hwmon: (pmbus/max31827) Explain why enum chips must not start with 0

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Date: Tue, 11 Jun 2024 11:07:10 +0200
From: Nuno Sá <noname.nuno@...il.com>
To: Guenter Roeck <linux@...ck-us.net>, linux-hwmon@...r.kernel.org
Cc: Rob Herring <robh@...nel.org>, linux-kernel@...r.kernel.org, Peter Yin
 <peteryin.openbmc@...il.com>, Potin Lai <potin.lai.pt@...il.com>, Daniel
 Matyas <daniel.matyas@...log.com>, Andrew Davis <afd@...com>, Krzysztof
 Kozlowski <krzysztof.kozlowski@...aro.org>
Subject: Re: [PATCH 4/4] hwmon: (pmbus/max31827) Explain why enum chips must
 not start with 0

On Mon, 2024-06-10 at 11:10 -0700, Guenter Roeck wrote:
> If a driver calls device_get_match_data(), the .data pointer in its id
> data structures must not be NULL/0 because device_get_match_data()
> returns NULL if an entry is not found. Explain that in a comment to avoid
> confusion why this is required in this driver but not in other drivers.
> 
> Cc: Daniel Matyas <daniel.matyas@...log.com>
> Signed-off-by: Guenter Roeck <linux@...ck-us.net>
> ---

Acked-by: Nuno Sa <nuno.sa@...log.com>

>  drivers/hwmon/max31827.c | 5 +++++
>  1 file changed, 5 insertions(+)
> 
> diff --git a/drivers/hwmon/max31827.c b/drivers/hwmon/max31827.c
> index f8a13b30f100..391cb059e94d 100644
> --- a/drivers/hwmon/max31827.c
> +++ b/drivers/hwmon/max31827.c
> @@ -46,6 +46,11 @@
>  #define MAX31827_M_DGR_TO_16_BIT(x)	(((x) << 4) / 1000)
>  #define MAX31827_DEVICE_ENABLE(x)	((x) ? 0xA : 0x0)
>  
> +/*
> + * The enum passed in the .data pointer of struct of_device_id must
> + * start with a value != 0 since that is a requirement for using
> + * device_get_match_data().
> + */
>  enum chips { max31827 = 1, max31828, max31829 };
>  
>  enum max31827_cnv {