Subject: [PATCH 1/8] firmware: arm_scmi: improve code readability using bitfield accessor macros

From: [email-masked] (Jonathan Cameron)
Date: Thu, 17 May 2018 09:14:33 +0100

On Wed, 9 May 2018 18:07:07 +0100
Sudeep Holla <[email-masked]> wrote:

> By using FIELD_{FIT,GET,PREP} and GENMASK macro accessors we can avoid
> some clumpsy custom shifting and masking macros and also improve the
> code better readability.
> 
> Signed-off-by: Sudeep Holla <[email-masked]>
Hi Sudeep,

A minor comment inline.

Jonathan
> ---
>  drivers/firmware/arm_scmi/common.h |  9 +++++----
>  drivers/firmware/arm_scmi/driver.c | 31 ++++++++++++++-----------------
>  2 files changed, 19 insertions(+), 21 deletions(-)
> 
> diff --git a/drivers/firmware/arm_scmi/common.h b/drivers/firmware/arm_scmi/common.h
> index 0c30234f9098..e8f332c9c469 100644
> --- a/drivers/firmware/arm_scmi/common.h
> +++ b/drivers/firmware/arm_scmi/common.h
> @@ -7,6 +7,7 @@
>   * Copyright (C) 2018 ARM Ltd.
>   */
>  
> +#include <linux/bitfield.h>
>  #include <linux/completion.h>
>  #include <linux/device.h>
>  #include <linux/errno.h>
> @@ -14,10 +15,10 @@
>  #include <linux/scmi_protocol.h>
>  #include <linux/types.h>
>  
> -#define PROTOCOL_REV_MINOR_BITS	16
> -#define PROTOCOL_REV_MINOR_MASK	((1U << PROTOCOL_REV_MINOR_BITS) - 1)
> -#define PROTOCOL_REV_MAJOR(x)	((x) >> PROTOCOL_REV_MINOR_BITS)
> -#define PROTOCOL_REV_MINOR(x)	((x) & PROTOCOL_REV_MINOR_MASK)
> +#define PROTOCOL_REV_MINOR_MASK	GENMASK(15, 0)
> +#define PROTOCOL_REV_MAJOR_MASK	GENMASK(31, 16)
> +#define PROTOCOL_REV_MAJOR(x)	(u16)(FIELD_GET(PROTOCOL_REV_MAJOR_MASK, (x)))
> +#define PROTOCOL_REV_MINOR(x)	(u16)(FIELD_GET(PROTOCOL_REV_MINOR_MASK, (x)))
>  #define MAX_PROTOCOLS_IMP	16
>  #define MAX_OPPS		16
>  
> diff --git a/drivers/firmware/arm_scmi/driver.c b/drivers/firmware/arm_scmi/driver.c
> index 14b147135a0c..917786d91f55 100644
> --- a/drivers/firmware/arm_scmi/driver.c
> +++ b/drivers/firmware/arm_scmi/driver.c
> @@ -29,16 +29,12 @@
>  
>  #include "common.h"
>  
> -#define MSG_ID_SHIFT		0
> -#define MSG_ID_MASK		0xff
> -#define MSG_TYPE_SHIFT		8
> -#define MSG_TYPE_MASK		0x3
> -#define MSG_PROTOCOL_ID_SHIFT	10
> -#define MSG_PROTOCOL_ID_MASK	0xff
> -#define MSG_TOKEN_ID_SHIFT	18
> -#define MSG_TOKEN_ID_MASK	0x3ff
> -#define MSG_XTRACT_TOKEN(header)	\
> -	(((header) >> MSG_TOKEN_ID_SHIFT) & MSG_TOKEN_ID_MASK)
> +#define MSG_ID_MASK		GENMASK(7, 0)
> +#define MSG_TYPE_MASK		GENMASK(9, 8)
> +#define MSG_PROTOCOL_ID_MASK	GENMASK(17, 10)
> +#define MSG_TOKEN_ID_MASK	GENMASK(27, 18)
> +#define MSG_XTRACT_TOKEN(hdr)	FIELD_GET(MSG_TOKEN_ID_MASK, (hdr))
> +#define MSG_TOKEN_MAX		(MSG_XTRACT_TOKEN(MSG_TOKEN_ID_MASK) + 1)

This feels a little odd. It's not the Max value, I think, but rather one more than
it. I would set it to this -1 and use > than in the test below.

>  
>  enum scmi_error_codes {
>  	SCMI_SUCCESS = 0,	/* Success */
> @@ -255,9 +251,9 @@ static void scmi_rx_callback(struct mbox_client *cl, void *m)
>   */
>  static inline u32 pack_scmi_header(struct scmi_msg_hdr *hdr)
>  {
> -	return ((hdr->id & MSG_ID_MASK) << MSG_ID_SHIFT) |
> -	   ((hdr->seq & MSG_TOKEN_ID_MASK) << MSG_TOKEN_ID_SHIFT) |
> -	   ((hdr->protocol_id & MSG_PROTOCOL_ID_MASK) << MSG_PROTOCOL_ID_SHIFT);
> +	return FIELD_PREP(MSG_ID_MASK, hdr->id) |
> +		FIELD_PREP(MSG_TOKEN_ID_MASK, hdr->seq) |
> +		FIELD_PREP(MSG_PROTOCOL_ID_MASK, hdr->protocol_id);
>  }
>  
>  /**
> @@ -621,9 +617,9 @@ static int scmi_xfer_info_init(struct scmi_info *sinfo)
>  	struct scmi_xfers_info *info = &sinfo->minfo;
>  
>  	/* Pre-allocated messages, no more than what hdr.seq can support */
> -	if (WARN_ON(desc->max_msg >= (MSG_TOKEN_ID_MASK + 1))) {
> -		dev_err(dev, "Maximum message of %d exceeds supported %d\n",
> -			desc->max_msg, MSG_TOKEN_ID_MASK + 1);
> +	if (WARN_ON(desc->max_msg >= MSG_TOKEN_MAX)) {

> +		dev_err(dev, "Maximum message of %d exceeds supported %ld\n",
> +			desc->max_msg, MSG_TOKEN_MAX);
>  		return -EINVAL;
>  	}
>  
> @@ -840,7 +836,8 @@ static int scmi_probe(struct platform_device *pdev)
>  		if (of_property_read_u32(child, "reg", &prot_id))
>  			continue;
>  
> -		prot_id &= MSG_PROTOCOL_ID_MASK;
> +		if (!FIELD_FIT(MSG_PROTOCOL_ID_MASK, prot_id))
> +			dev_err(dev, "Out of range protocol %d\n", prot_id);
>  
>  		if (!scmi_is_protocol_implemented(handle, prot_id)) {
>  			dev_err(dev, "SCMI protocol %d not implemented\n",