Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 2620:137:e000::1:20 as permitted sender) client-ip=2620:137:e000::1:20;
Message-ID: <69d8ad0e-efc6-f37d-9aa7-d06f8de16a6a@redhat.com>
Date:   Thu, 9 Jun 2022 15:09:21 +0200
MIME-Version: 1.0
User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:91.0) Gecko/20100101
 Thunderbird/91.10.0
Subject: Re: [PATCH v6 5/5] fbdev: Make registered_fb[] private to fbmem.c
Content-Language: en-US
To:     Thomas Zimmermann <tzimmermann@suse.de>,
        linux-kernel@vger.kernel.org
Cc:     dri-devel@lists.freedesktop.org, Laszlo Ersek <lersek@redhat.com>,
        Alex Williamson <alex.williamson@redhat.com>,
        Gerd Hoffmann <kraxel@redhat.com>, kvm@vger.kernel.org,
        Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        Daniel Vetter <daniel.vetter@ffwll.ch>,
        kernel test robot <lkp@intel.com>,
        Jens Frederich <jfrederich@gmail.com>,
        Jon Nettleton <jon.nettleton@gmail.com>,
        linux-staging@lists.linux.dev,
        Daniel Vetter <daniel.vetter@intel.com>,
        Daniel Vetter <daniel@ffwll.ch>, Helge Deller <deller@gmx.de>,
        Matthew Wilcox <willy@infradead.org>,
        Sam Ravnborg <sam@ravnborg.org>,
        Tetsuo Handa <penguin-kernel@i-love.sakura.ne.jp>,
        Zhen Lei <thunder.leizhen@huawei.com>,
        Alex Deucher <alexander.deucher@amd.com>,
        Xiyu Yang <xiyuyang19@fudan.edu.cn>,
        linux-fbdev@vger.kernel.org, Zheyu Ma <zheyuma97@gmail.com>,
        Guenter Roeck <linux@roeck-us.net>
References: <20220607182338.344270-1-javierm@redhat.com>
 <20220607182338.344270-6-javierm@redhat.com>
 <3ebac271-1276-8132-6175-ca95a26cfcbb@suse.de>
From:   Javier Martinez Canillas <javierm@redhat.com>
In-Reply-To: <3ebac271-1276-8132-6175-ca95a26cfcbb@suse.de>
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 7bit
Precedence: bulk

Hello Thomas,

On 6/9/22 13:49, Thomas Zimmermann wrote:
> Hi Javier
> 
> Am 07.06.22 um 20:23 schrieb Javier Martinez Canillas:
>> From: Daniel Vetter <daniel.vetter@ffwll.ch>
>>
>> Well except when the olpc dcon fbdev driver is enabled, that thing
>> digs around in there in rather unfixable ways.
> 
> There is fb_client_register() to set up a 'client' on top of an fbdev. 
> The client would then get messages about modesetting, blanks, removals, 
> etc. But you'd probably need an OLPC to convert dcon, and the mechanism 
> itself is somewhat unloved these days.
> 
> Your patch complicates the fbdev code AFAICT. So I'd either drop it or, 
> even better, build a nicer interface for dcon.
> 
> The dcon driver appears to look only at the first entry. Maybe add 
> fb_info_get_by_index() and fb_info_put() and export those. They would be 
> trivial wrappers somewhere in fbmem.c:
> 
> #if IS_ENABLED(CONFIG_FB_OLPC_DCON)
> struct fb_info *fb_info_get_by_index(unsigned int index)
> {
> 	return get_fb_info(index);
> }
> EXPORT_SYMBOL()
> void fb_info_put(struct fb_info *fb_info)
> {
> 	put_fb_info(fb_info);
> }
> EXPORT_SYMBOL()
> #endif
> 
> In dcon itself, using the new interfaces will actually acquire a 
> reference to keep the display alive. The code at [1] could be replaced. 
> And a call to fb_info_put() needs to go into dcon_remove(). [2]
> 

Thanks for your suggestions, that makes sense to me. I'll drop this
patch from the set and post as a follow-up a different approach as
you suggested.

-- 
Best regards,

Javier Martinez Canillas
Linux Engineering
Red Hat