linux-kernel - Re: [PATCH] usb: ehci: replace scnprintf() with sysfs

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Message-ID: <d2d321cd-7ca7-42d9-8eb8-7ab639dddfa6@wanadoo.fr>
Date: Fri, 20 Jun 2025 21:56:09 +0200
From: Christophe JAILLET <christophe.jaillet@...adoo.fr>
To: Hendrik Hamerlinck <hendrik.hamerlinck@...mernet.be>,
 stern@...land.harvard.edu, gregkh@...uxfoundation.org
Cc: skhan@...uxfoundation.org, linux-kernel-mentees@...ts.linux.dev,
 linux-usb@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] usb: ehci: replace scnprintf() with sysfs_emit()

Le 19/06/2025 à 14:07, Hendrik Hamerlinck a écrit :
> Per Documentation/filesystems/sysfs.rst, show() methods should only
> use sysfs_emit() or sysfs_emit_at() when formatting values to be
> returned to userspace.
> 
> Convert the uses of scnprintf() in sysfs show() methods to
> sysfs_emit() and sysfs_emit_at() for better safety and consistency.
> 
> Signed-off-by: Hendrik Hamerlinck <hendrik.hamerlinck@...mernet.be>
> ---
>   drivers/usb/host/ehci-sysfs.c | 15 +++++----------
>   1 file changed, 5 insertions(+), 10 deletions(-)
> 
> diff --git a/drivers/usb/host/ehci-sysfs.c b/drivers/usb/host/ehci-sysfs.c
> index 8f75cb7b197c..3786e81b0ed9 100644
> --- a/drivers/usb/host/ehci-sysfs.c
> +++ b/drivers/usb/host/ehci-sysfs.c
> @@ -12,21 +12,18 @@ static ssize_t companion_show(struct device *dev,
>   			      char *buf)
>   {
>   	struct ehci_hcd		*ehci;
> -	int			nports, index, n;
> -	int			count = PAGE_SIZE;
> -	char			*ptr = buf;
> +	int			nports, index;
> +	int			len = 0;
>   
>   	ehci = hcd_to_ehci(dev_get_drvdata(dev));
>   	nports = HCS_N_PORTS(ehci->hcs_params);
>   
>   	for (index = 0; index < nports; ++index) {
>   		if (test_bit(index, &ehci->companion_ports)) {
> -			n = scnprintf(ptr, count, "%d\n", index + 1);
> -			ptr += n;
> -			count -= n;
> +			len += sysfs_emit_at(buf, len, "%d\n", index + 1);
>   		}

Nitpick: extra { } looks useless now.

>   	}
> -	return ptr - buf;
> +	return len;
>   }
>   
>   /*
> @@ -70,11 +67,9 @@ static ssize_t uframe_periodic_max_show(struct device *dev,
>   					char *buf)
>   {
>   	struct ehci_hcd		*ehci;
> -	int			n;
>   
>   	ehci = hcd_to_ehci(dev_get_drvdata(dev));
> -	n = scnprintf(buf, PAGE_SIZE, "%d\n", ehci->uframe_periodic_max);
> -	return n;
> +	return sysfs_emit(buf, "%d\n", ehci->uframe_periodic_max);
>   }
>   
>