linux-kernel - Re: [PATCH v3 6/6] iio: adc: ad7173: Reduce device info struct size

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Date: Wed, 29 May 2024 14:23:44 +0200
From: Nuno Sá <noname.nuno@...il.com>
To: dumitru.ceclan@...log.com
Cc: Lars-Peter Clausen <lars@...afoo.de>, Michael Hennerich
 <Michael.Hennerich@...log.com>, Jonathan Cameron <jic23@...nel.org>, Rob
 Herring <robh@...nel.org>, Krzysztof Kozlowski
 <krzysztof.kozlowski+dt@...aro.org>, Conor Dooley <conor+dt@...nel.org>,
 David Lechner <dlechner@...libre.com>,  linux-iio@...r.kernel.org,
 devicetree@...r.kernel.org,  linux-kernel@...r.kernel.org, Dumitru Ceclan
 <mitrutzceclan@...il.com>
Subject: Re: [PATCH v3 6/6] iio: adc: ad7173: Reduce device info struct size

On Mon, 2024-05-27 at 20:02 +0300, Dumitru Ceclan via B4 Relay wrote:
> From: Dumitru Ceclan <dumitru.ceclan@...log.com>
> 
> Reduce the size used by the device info struct by packing the bool
>  fields within the same byte. This reduces the struct size from 52 bytes
>  to 44 bytes.
> 
> Signed-off-by: Dumitru Ceclan <dumitru.ceclan@...log.com>
> ---
>  drivers/iio/adc/ad7173.c | 16 ++++++++--------
>  1 file changed, 8 insertions(+), 8 deletions(-)
> 
> diff --git a/drivers/iio/adc/ad7173.c b/drivers/iio/adc/ad7173.c
> index 328685ce25e0..e8357a21d513 100644
> --- a/drivers/iio/adc/ad7173.c
> +++ b/drivers/iio/adc/ad7173.c
> @@ -179,15 +179,15 @@ struct ad7173_device_info {
>  	unsigned int clock;
>  	unsigned int id;
>  	char *name;
> -	bool has_current_inputs;
> -	bool has_vcom_input;
> -	bool has_temp;
> +	bool has_current_inputs		:1;
> +	bool has_vcom_input		:1;
> +	bool has_temp			:1;
>  	/* ((AVDD1 − AVSS)/5) */
> -	bool has_common_input;
> -	bool has_input_buf;
> -	bool has_int_ref;
> -	bool has_ref2;
> -	bool higher_gpio_bits;
> +	bool has_common_input		:1;
> +	bool has_input_buf		:1;
> +	bool has_int_ref		:1;
> +	bool has_ref2			:1;
> +	bool higher_gpio_bits		:1;
>  	u8 num_gpios;
>  };
>  
> 

This is really a very micro optimization... I would drop it tbh but no strong
feelings about it.

- Nuno Sá