linux-kernel - Re: [PATCH v2] tpm: Replace scnprintf() with sysfs_emit() and sysfs_emit

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Message-ID: <3c63b547-d3fc-40b8-9b7d-61660dc89425@wanadoo.fr>
Date: Sat, 21 Jun 2025 07:13:56 +0200
From: Christophe JAILLET <christophe.jaillet@...adoo.fr>
To: Chelsy Ratnawat <chelsyratnawat2001@...il.com>, peterhuewe@....de,
 jarkko@...nel.org
Cc: jgg@...pe.ca, linux-integrity@...r.kernel.org,
 linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2] tpm: Replace scnprintf() with sysfs_emit() and
 sysfs_emit_at() in sysfs show functions

Le 19/06/2025 à 15:13, Chelsy Ratnawat a écrit :
> Replace calls to scnprintf() with sysfs_emit() and sysfs_emit_at() in
> sysfs show functions. These helpers are preferred in sysfs callbacks
> because they automatically handle buffer sizing (PAGE_SIZE) and
> improve safety and readability.
> 
> Signed-off-by: Chelsy Ratnawat <chelsyratnawat2001@...il.com>
> ---
> Changes in v2:
> - Corrected sysfs_emit_at() usage to pass buf as first argument
> 
>   drivers/char/tpm/tpm_ppi.c | 26 +++++++++++++-------------
>   1 file changed, 13 insertions(+), 13 deletions(-)
> 
> diff --git a/drivers/char/tpm/tpm_ppi.c b/drivers/char/tpm/tpm_ppi.c
> index bc7b1b4501b3..2c0d1859284d 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,
> @@ -87,11 +87,11 @@ 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,
> +				size = sysfs_emit(buf,
>   				    "%llu %llu\n", req,
>   				    obj->package.elements[2].integer.value);
>   			else
> -				size = scnprintf(buf, PAGE_SIZE,
> +				size = sysfs_emit(buf,
>   						"%llu\n", req);

Nitpick: Can fit on the same line now

>   		}
>   	} else if (obj->package.count == 2 &&
> @@ -100,7 +100,7 @@ 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",
> +			size = sysfs_emit(buf, "%llu\n",
>   				 obj->package.elements[1].integer.value);
>   	}
>   
> @@ -211,9 +211,9 @@ 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,
> +		status = sysfs_emit(buf, "%d: %s\n", ret,
>   				   info[ARRAY_SIZE(info)-1]);

Nitpick: Alignment could be updated (same for others below)

>   	return status;
>   }
> @@ -255,22 +255,22 @@ 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,
> +			status = sysfs_emit(buf, "%llu %s\n", req,
>   					   "0: Success");
>   		else if (res == 0xFFFFFFF0)
> -			status = scnprintf(buf, PAGE_SIZE, "%llu %s\n", req,
> +			status = sysfs_emit(buf, "%llu %s\n", req,
>   					   "0xFFFFFFF0: User Abort");
>   		else if (res == 0xFFFFFFF1)
> -			status = scnprintf(buf, PAGE_SIZE, "%llu %s\n", req,
> +			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",
> +			status = sysfs_emit(buf, "%llu %llu: %s\n",
>   					   req, res, "Corresponding TPM error");
>   		else
> -			status = scnprintf(buf, PAGE_SIZE, "%llu %llu: %s\n",
> +			status = sysfs_emit(buf, "%llu %llu: %s\n",
>   					   req, res, "Error");
>   	} else {
> -		status = scnprintf(buf, PAGE_SIZE, "%llu: %s\n",
> +		status = sysfs_emit(buf, "%llu: %s\n",
>   				   req, "No Recent Request");
>   	}
>   
> @@ -314,7 +314,7 @@ 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",
> +			str += sysfs_emit_at(buf, str - buf, "%d %d: %s\n",
>   					 i, ret, info[ret]);

You should remove 'str' and use an int for the length instead.
This would be much standard.

 > git grep sysfs_emit_at[^,]*,[^,-]*-
does not find any such pointer manipulation to compute the length.

CJ



>   	}
>