Received-SPF: softfail (google.com: domain of transitioning linux-kernel-owner@vger.kernel.org does not designate 23.128.96.19 as permitted sender) client-ip=23.128.96.19;
Message-ID: <97339148-9876-cfc1-8df8-dbb21a9c3c7c@redhat.com>
Date:   Fri, 29 Apr 2022 10:06:52 +0200
MIME-Version: 1.0
User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:91.0) Gecko/20100101
 Thunderbird/91.8.0
Subject: Re: [PATCH v3 0/5] Fix some race conditions that exists between fbmem
 and sysfb
Content-Language: en-US
To:     Thomas Zimmermann <tzimmermann@suse.de>,
        linux-kernel@vger.kernel.org,
        Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        dri-devel@lists.freedesktop.org,
        Alex Deucher <alexander.deucher@amd.com>,
        Borislav Petkov <bp@suse.de>,
        Changcheng Deng <deng.changcheng@zte.com.cn>,
        Hans de Goede <hdegoede@redhat.com>,
        Helge Deller <deller@gmx.de>, Johan Hovold <johan@kernel.org>,
        Jonathan Corbet <corbet@lwn.net>,
        Miaoqian Lin <linmq006@gmail.com>,
        Peter Jones <pjones@redhat.com>,
        Sam Ravnborg <sam@ravnborg.org>,
        Tetsuo Handa <penguin-kernel@i-love.sakura.ne.jp>,
        Yizhuo Zhai <yzhai003@ucr.edu>,
        Zhen Lei <thunder.leizhen@huawei.com>,
        linux-doc@vger.kernel.org, linux-fbdev@vger.kernel.org
References: <20220420085303.100654-1-javierm@redhat.com>
 <535ebbe4-605c-daf5-1afb-f5225e4bb3a8@suse.de>
 <093d742f-4c87-2ff3-e9fe-153cd734f8e4@suse.de>
 <220929be-91c4-d19c-b04f-312c5f7e9e40@redhat.com>
 <YmuYE2t51lPIRT8p@phenom.ffwll.local>
From:   Javier Martinez Canillas <javierm@redhat.com>
In-Reply-To: <YmuYE2t51lPIRT8p@phenom.ffwll.local>
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 7bit
Precedence: bulk

Hello Daniel,

On 4/29/22 09:47, Daniel Vetter wrote:

[snip]

>>
>> Exactly, should be done when the device is registered rather than when
>> the driver is registered or a call is made to remove the conflicting FB.
>>
>> I'll rework this series with only the bits for sysfb_disable() and drop
>> the rest. We can go back to the discussion of the remaining parts later
>> if that makes sense (I still think that patch 3/5 is a better approach,
>> but let's defer that for a different series).
> 
> We need to kill sysfb _before_ the driver loads, otherwise you can have
> two drivers fighting over each another. And yes that means you might end
> up with black screen if the driver load goes wrong, but the two drivers
> fighting over each another can also result in black screens. And the
> latter isn't fixable any other way (in general at least) than by making
> sure the fw stuff is gone before driver load starts in earnest.

Yes, you are correct. I didn't realize all the possible cases when agreed
with Thomas about doing this but tried and found that it's not enough.

I've a full patch-set now and will post as a RFC so we can discuss more.

> -Daniel

-- 
Best regards,

Javier Martinez Canillas
Linux Engineering
Red Hat