linux-kernel - Re: [PATCH v5] tpm: Replace scnprintf() with sysfs_emit() and sysfs_emit

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Message-ID: <aGWmV6DLiIc8f7N6@kernel.org>
Date: Thu, 3 Jul 2025 00:36:23 +0300
From: Jarkko Sakkinen <jarkko@...nel.org>
To: Chelsy Ratnawat <chelsyratnawat2001@...il.com>
Cc: peterhuewe@....de, jgg@...pe.ca, linux-integrity@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH v5] tpm: Replace scnprintf() with sysfs_emit() and
 sysfs_emit_at() in sysfs show functions

On Thu, Jun 26, 2025 at 05:51:30AM -0700, Chelsy Ratnawat wrote:
> Documentation/filesystems/sysfs.rst mentions that show() should only
> use sysfs_emit() or sysfs_emit_at() when formating the value to be
> returned to user space. So replace scnprintf() with sysfs_emit().
> 
> Signed-off-by: Chelsy Ratnawat <chelsyratnawat2001@...il.com>
> ---
> Changes in v5 : 
> - Fix alignment and coding style problems
> 
>  drivers/char/tpm/tpm_ppi.c | 52 ++++++++++++++++++--------------------
>  1 file changed, 25 insertions(+), 27 deletions(-)
> 
> diff --git a/drivers/char/tpm/tpm_ppi.c b/drivers/char/tpm/tpm_ppi.c
> index bc7b1b4501b3..d53fce1c9d6f 100644
> --- a/drivers/char/tpm/tpm_ppi.c
> +++ b/drivers/char/tpm/tpm_ppi.c
> @@ -52,7 +52,7 @@ static ssize_t tpm_show_ppi_version(struct device *dev,
>  {
>  	struct tpm_chip *chip = to_tpm_chip(dev);
>  
> -	return scnprintf(buf, PAGE_SIZE, "%s\n", chip->ppi_version);
> +	return sysfs_emit(buf, "%s\n", chip->ppi_version);
>  }
>  
>  static ssize_t tpm_show_ppi_request(struct device *dev,
> @@ -87,12 +87,10 @@ static ssize_t tpm_show_ppi_request(struct device *dev,
>  		else {
>  			req = obj->package.elements[1].integer.value;
>  			if (tpm_ppi_req_has_parameter(req))
> -				size = scnprintf(buf, PAGE_SIZE,
> -				    "%llu %llu\n", req,
> -				    obj->package.elements[2].integer.value);
> +				size = sysfs_emit(buf, "%llu %llu\n", req,
> +						  obj->package.elements[2].integer.value);
>  			else
> -				size = scnprintf(buf, PAGE_SIZE,
> -						"%llu\n", req);
> +				size = sysfs_emit(buf, "%llu\n", req);
>  		}
>  	} else if (obj->package.count == 2 &&
>  	    obj->package.elements[0].type == ACPI_TYPE_INTEGER &&
> @@ -100,8 +98,8 @@ static ssize_t tpm_show_ppi_request(struct device *dev,
>  		if (obj->package.elements[0].integer.value)
>  			size = -EFAULT;
>  		else
> -			size = scnprintf(buf, PAGE_SIZE, "%llu\n",
> -				 obj->package.elements[1].integer.value);
> +			size = sysfs_emit(buf, "%llu\n",
> +					  obj->package.elements[1].integer.value);
>  	}
>  
>  	ACPI_FREE(obj);
> @@ -211,10 +209,10 @@ static ssize_t tpm_show_ppi_transition_action(struct device *dev,
>  	}
>  
>  	if (ret < ARRAY_SIZE(info) - 1)
> -		status = scnprintf(buf, PAGE_SIZE, "%d: %s\n", ret, info[ret]);
> +		status = sysfs_emit(buf, "%d: %s\n", ret, info[ret]);
>  	else
> -		status = scnprintf(buf, PAGE_SIZE, "%d: %s\n", ret,
> -				   info[ARRAY_SIZE(info)-1]);
> +		status = sysfs_emit(buf, "%d: %s\n", ret,
> +				    info[ARRAY_SIZE(info) - 1]);
>  	return status;
>  }
>  
> @@ -255,23 +253,23 @@ static ssize_t tpm_show_ppi_response(struct device *dev,
>  	res = ret_obj[2].integer.value;
>  	if (req) {
>  		if (res == 0)
> -			status = scnprintf(buf, PAGE_SIZE, "%llu %s\n", req,
> -					   "0: Success");
> +			status = sysfs_emit(buf, "%llu %s\n", req,
> +					    "0: Success");
>  		else if (res == 0xFFFFFFF0)
> -			status = scnprintf(buf, PAGE_SIZE, "%llu %s\n", req,
> -					   "0xFFFFFFF0: User Abort");
> +			status = sysfs_emit(buf, "%llu %s\n", req,
> +					    "0xFFFFFFF0: User Abort");
>  		else if (res == 0xFFFFFFF1)
> -			status = scnprintf(buf, PAGE_SIZE, "%llu %s\n", req,
> -					   "0xFFFFFFF1: BIOS Failure");
> +			status = sysfs_emit(buf, "%llu %s\n", req,
> +					    "0xFFFFFFF1: BIOS Failure");
>  		else if (res >= 1 && res <= 0x00000FFF)
> -			status = scnprintf(buf, PAGE_SIZE, "%llu %llu: %s\n",
> -					   req, res, "Corresponding TPM error");
> +			status = sysfs_emit(buf, "%llu %llu: %s\n",
> +					    req, res, "Corresponding TPM error");
>  		else
> -			status = scnprintf(buf, PAGE_SIZE, "%llu %llu: %s\n",
> -					   req, res, "Error");
> +			status = sysfs_emit(buf, "%llu %llu: %s\n",
> +					    req, res, "Error");
>  	} else {
> -		status = scnprintf(buf, PAGE_SIZE, "%llu: %s\n",
> -				   req, "No Recent Request");
> +		status = sysfs_emit(buf, "%llu: %s\n",
> +				    req, "No Recent Request");
>  	}
>  
>  cleanup:
> @@ -284,7 +282,7 @@ static ssize_t show_ppi_operations(acpi_handle dev_handle, char *buf, u32 start,
>  {
>  	int i;
>  	u32 ret;
> -	char *str = buf;
> +	int len = 0;
>  	union acpi_object *obj, tmp;
>  	union acpi_object argv = ACPI_INIT_DSM_ARGV4(1, &tmp);
>  
> @@ -314,11 +312,11 @@ static ssize_t show_ppi_operations(acpi_handle dev_handle, char *buf, u32 start,
>  		}
>  
>  		if (ret > 0 && ret < ARRAY_SIZE(info))
> -			str += scnprintf(str, PAGE_SIZE, "%d %d: %s\n",
> -					 i, ret, info[ret]);
> +			len += sysfs_emit_at(buf, len, "%d %d: %s\n",
> +					     i, ret, info[ret]);
>  	}
>  
> -	return str - buf;
> +	return len;
>  }
>  
>  static ssize_t tpm_show_ppi_tcg_operations(struct device *dev,
> -- 
> 2.47.1
> 

Looks good to me.

Reviewed-by: Jarkko Sakkinen <jarkko@...nel.org>

BR, Jarkko