linux-kernel - Re: [PATCH] scsi: ufs: sysfs: add is_ascii

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Message-ID: <YCjzKOEV9fUPf3Ja@kroah.com>
Date:   Sun, 14 Feb 2021 10:53:44 +0100
From:   Greg KH <gregkh@...uxfoundation.org>
To:     Bart Van Assche <bvanassche@....org>
Cc:     Arthur Simchaev <Arthur.Simchaev@...disk.com>,
        "James E . J . Bottomley" <jejb@...ux.vnet.ibm.com>,
        "Martin K . Petersen" <martin.petersen@...cle.com>,
        linux-scsi@...r.kernel.org, linux-kernel@...r.kernel.org,
        alim.akhtar@...sung.com, Bean Huo <beanhuo@...ron.com>,
        Arthur Simchaev <arthur.simchaev@....com>
Subject: Re: [PATCH] scsi: ufs: sysfs: add is_ascii_output entry

On Wed, Feb 10, 2021 at 07:35:25PM -0800, Bart Van Assche wrote:
> On 2/10/21 2:53 AM, Arthur Simchaev wrote:
> > +static bool is_ascii_output = true;
> 
> [ ... ]
> 
> >  static const char *ufschd_uic_link_state_to_string(
> >  			enum uic_link_state state)
> >  {
> > @@ -693,7 +695,15 @@ static ssize_t _name##_show(struct device *dev,				\
> >  				      SD_ASCII_STD);			\
> >  	if (ret < 0)							\
> >  		goto out;						\
> > -	ret = sysfs_emit(buf, "%s\n", desc_buf);			\
> > +	if (is_ascii_output) {						\
> > +		ret = sysfs_emit(buf, "%s\n", desc_buf);		\
> > +	} else {							\
> > +		int i;							\
> > +									\
> > +		for (i = 0; i < desc_buf[0]; i++)			\
> > +			hex_byte_pack(buf + i * 2, desc_buf[i]);	\
> > +		ret = sysfs_emit(buf, "%s\n", buf);			\
> > +	}								\
> >  out:									\
> >  	pm_runtime_put_sync(hba->dev);					\
> >  	kfree(desc_buf);						\
> 
> Please do not introduce a mode variable but instead introduce a new
> attribute such that there is one attribute for the unicode output and
> one attribute for the ASCII output. Mode variables are troublesome when
> e.g. two scripts try to set the mode attribute concurrently.

Agreed, just make a new sysfs file, please never change the output of an
existing sysfs file, that way will guarantee confusion in userspace.

thanks,

greg k-h