linux-kernel - Re: [PATCH v3 6/8] platform/x86: dell-wmi-smbios: Add a sysfs interface for SMBIOS tokens

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Message-ID: <CAHp75Vf34xOgBSNPxwUrGatX_+cWOP_gG3zurzBmeGWh+Duhhg@mail.gmail.com>
Date:   Sun, 1 Oct 2017 11:51:52 +0300
From:   Andy Shevchenko <andy.shevchenko@...il.com>
To:     Darren Hart <dvhart@...radead.org>
Cc:     Mario Limonciello <mario.limonciello@...l.com>,
        LKML <linux-kernel@...r.kernel.org>,
        Platform Driver <platform-driver-x86@...r.kernel.org>,
        Andy Lutomirski <luto@...nel.org>, quasisec@...gle.com,
        Pali Rohár <pali.rohar@...il.com>
Subject: Re: [PATCH v3 6/8] platform/x86: dell-wmi-smbios: Add a sysfs
 interface for SMBIOS tokens

On Sat, Sep 30, 2017 at 5:10 AM, Darren Hart <dvhart@...radead.org> wrote:
> On Wed, Sep 27, 2017 at 11:02:18PM -0500, Mario Limonciello wrote:
>> Currently userspace tools can access system tokens via the dcdbas
>> kernel module and a SMI call that will cause the platform to execute
>> SMM code.
>>
>> With a goal in mind of deprecating the dcdbas kernel module a different
>> method for accessing these tokens from userspace needs to be created.
>>
>> This is intentionally marked to only be readable as root as it can
>> contain sensitive information about the platform's configuration.
>>
>> Signed-off-by: Mario Limonciello <mario.limonciello@...l.com>
>> ---
> ...
>> +static ssize_t tokens_show(struct device *dev,
>> +                        struct device_attribute *attr, char *buf)
>> +{
>> +     size_t off = 0;
>> +     int i;
>> +
>> +     for (i = 0; i < da_num_tokens; i++) {
>> +             if (off > PAGE_SIZE)
>> +                     break;
>> +             off += scnprintf(buf+off, PAGE_SIZE-off, "%04x\t%04x\t%04x\n",
>
> Minor Coding Style nit - spaces around binary operators: 3.1) Spaces

Fresh looking to this excerpt gives me an idea that we may actually
predict how many tokens to write beforehand. It makes output also
cleaner in a sense to not disrupt a last token in the middle.

Something like
tokens_to_print = min(da_num_tokens, (PAGE_SIZE  - 1) / 15);
?

-- 
With Best Regards,
Andy Shevchenko