linux-kernel - Re: [PATCH 3/6] edac, mce_amd_inj: Modify flags attrigute to use string arguments

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Date:	Fri, 29 May 2015 13:20:31 -0500
From:	Aravind Gopalakrishnan <aravind.gopalakrishnan@....com>
To:	Borislav Petkov <bp@...en8.de>
CC:	<dougthompson@...ssion.com>, <mchehab@....samsung.com>,
	<linux-edac@...r.kernel.org>, <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 3/6] edac, mce_amd_inj: Modify flags attrigute to use
 string arguments

On 5/29/2015 8:49 AM, Borislav Petkov wrote:
> On Wed, May 27, 2015 at 02:03:35PM -0500, Aravind Gopalakrishnan wrote:
>>   
>> +#define MAX_FLAG_OPT_SIZE	10
> Why 10?

No specific reason. Just an arbitrary max value that we won't hit right 
now or in the future.

> This should be 2 and increased when another, longer injection type
> string gets introduced.

Okay, I'll make it 2 here and will increase it to 3 in the next patch 
when I introduce injection types for the interrupts.

>
>>   
>> -	*val = m->inject_flags;
>> +	for (i = 0; i <= N_INJ_TYPES; i++) {
>> +		inj_op = flags_options[i];
>> +		if (inj_op && strncmp(inj_op, buf, cnt) == 0)
>> +			break;
>> +	}
> What's wrong with:
>
> 	for (i = 0; i < N_INJ_TYPES; i++) {
> 		if (!strncmp(flags_options[i], buf, strlen(flags_options[i]))) {
> 			inj_type = i;
> 			return 0;
> 		}
> 	}
>
> 	return -EINVAL;

Hmm. That should work. Will simplify it in the next version.
I think I had a NULL in flags_options[] to denote the invalid option.
With your simplification, that can be removed. I'll make that change too.

And the 'cnt' value that I used won't be necessary. So, will remove that 
from __set_inj() definition as well.

>> +static ssize_t flags_write(struct file *filp, const char __user *ubuf,
>> +			   size_t cnt, loff_t *ppos)
>> +{
>> +	char buf[MAX_FLAG_OPT_SIZE + 1];
>> +	int err;
>> +	size_t ret;
>> +
>> +	ret = cnt;
> You're assigning cnt to ret here...
>
>> +
>> +	if (cnt > MAX_FLAG_OPT_SIZE)
>> +		cnt = MAX_FLAG_OPT_SIZE;
> ... but correcting cnt afterwards. The assignment should be *after* that
> correction.

With the change to MAX_FLAG_OPT_SIZE to 2 (or 3 depending on the max 
size), this check is
really an error check.

Shall I make err = -EINVAL by default and return that here if the 
condition is not satisfied?

Thanks,
-Aravind.
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