linux-kernel - Re: [PATCH v16 06/11] fw_cfg: handle fw_cfg_read

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Message-ID: <CAMxuvaxAuB3mtq7--KA+cCrGZ-kJj9+9yrdiToYo9EoH-=AYHw@mail.gmail.com>
Date:   Thu, 1 Mar 2018 12:36:29 +0100
From:   Marc-André Lureau <marcandre.lureau@...hat.com>
To:     "Michael S. Tsirkin" <mst@...hat.com>
Cc:     Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Arnd Bergmann <arnd@...db.de>, Baoquan He <bhe@...hat.com>,
        Sergio Lopez Pascual <slp@...hat.com>,
        "Somlo, Gabriel" <somlo@....edu>, xiaolong.ye@...el.com
Subject: Re: [PATCH v16 06/11] fw_cfg: handle fw_cfg_read_blob() error

Hi

On Wed, Feb 28, 2018 at 6:32 PM, Michael S. Tsirkin <mst@...hat.com> wrote:
>> @@ -557,7 +566,10 @@ static int fw_cfg_sysfs_probe(struct platform_device *pdev)
>>               goto err_probe;
>>
>>       /* get revision number, add matching top-level attribute */
>> -     fw_cfg_read_blob(FW_CFG_ID, &rev, 0, sizeof(rev));
>> +     err = fw_cfg_read_blob(FW_CFG_ID, &rev, 0, sizeof(rev));
>> +     if (err < 0)
>> +             goto err_probe;
>> +
>>       fw_cfg_rev = le32_to_cpu(rev);
>>       err = sysfs_create_file(fw_cfg_top_ko, &fw_cfg_rev_attr.attr);
>>       if (err)
>
> So on this one, maybe we should just drop this attribute.
> Does anyone use it?
> Removing it will speed up boot slightly.

We can't skip reading FW_CFG_ID (rev) as we need it to check DMA
support. I don't mind if we remove the sysfs entry, but I doubt it
makes a difference in boot time.

>> --
>> 2.16.1.73.g5832b7e9f2