From: Max Staudt <mstaudt@suse.de>
To: b.zolnierkie@samsung.com, linux-fbdev@vger.kernel.org,
michal@markovi.net, sndirsch@suse.com, oneukum@suse.com,
tiwai@suse.com, dri-devel@lists.freedesktop.org,
linux-kernel@vger.kernel.org, bernhard.rosenkranzer@linaro.org,
philm@manjaro.org
Subject: Re: [RFC PATCH v2 03/13] bootsplash: Flush framebuffer after drawing
Date: Tue, 19 Dec 2017 14:34:22 +0100 [thread overview]
Message-ID: <8bbb0497-4a10-2f81-0040-6e7cd4e7353c@suse.de> (raw)
In-Reply-To: <20171219122313.GE26573@phenom.ffwll.local>
On 12/19/2017 01:23 PM, Daniel Vetter wrote:
> On Thu, Dec 14, 2017 at 04:36:49PM +0100, Max Staudt wrote:
>> 2) We need to go out of the way when a graphical application starts, and
>> come back when it's done. fbcon already has the logic for this, and
>> fbcon is also the thing we're trying to hide. So it seems natural to add
>> the splash on top of fbcon - at least for now.
>
> And this "automatically disappear" semantics is horribly ill-defined
> between fbdev and native kms. So you're not really solving a problem,
> you're just not noticing the hacks because they're one layer removed (in
> the fbdev emulation code).
That's a general complaint about fbcon and/or the fbdev emulation in KMS drivers, right?
I can't see how it relates to my bootsplash, as I'm just replacing fbcon's output, wherever fbcon desires to draw at the given moment, and in no other case.
So when a graphical application sets the VT mode to KD_GRAPHICS, we get a call to do_blank_screen(), and then fbcon -and thus the bootsplash- is muted. The ioctl API has always been like this, and it's not specific to the patch in question.
Similarly, when a graphical application allocates a framebuffer via the KMS ioctl()s, and selects it for scanout, the driver will display that instead of the framebuffer it has allocated internally for the fbdev emulation.
>> 3) I can't use DRM from the kernel, for the same reason for which there
>> is no "drmcon" to supplant fbcon: There is no interface to reserve
>> framebuffer memory from kernel space: To get memory for a framebuffer,
>> one needs to have a struct file that is passed through the DRM stack
>> down into the drivers.
>
> On recent kernels you only need a struct drm_file, not a struct file. That
> can be NULL. We've done this to make drmcon possible/easier.
Oh that's cool, I missed that. Thanks!
Maybe a fb2drm compat layer will become reality, after all.
The bootsplash code is fairly straightforward to port to a future drmcon, and I'm happy to make the changes once drmcon is available.
But for now, we only have fbcon. And a *lot* of FB drivers. And we want them to show a bootsplash instead of text. So that's where the bootsplash needs to hook into.
>> If this interface existed, then there could be a generic "fb2drm"
>> translation layer, and we would no longer need FB compatibility code in
>> each KMS driver. Actually, I tried to implement this translation layer a
>> year ago, and hit too many walls.
>
> We're pretty much there already I think. The reason it's not entirely gone
> is that there's some nasty interactions between drm and the fbdev
> emulation, and just having a pile of drivers that aren't too trivial to
> convert.
Sounds like the state of the art last year - drm_file in most cases, but struct file deep in the drivers :(
>> 4) I don't fully understand what you'd like me to do. Last time I tried
>> to add a new entry to the fbops struct (namely fb_open_adj_file()), you
>> told me not to touch the framebuffer subsystem anymore, as it is meant
>> to die and driver developers shall use KMS instead. Have I
>> misunderstood?
>
> I still don't like anyone adding features to fbdev :-)
So I must not touch fbops, correct?
>> Something like fb->flush() to finish kernel space accesses would be nice
>> to have, but would need to be implemented for all affected drivers
>> separately. The copy op hack is ugly, but solves the problem
>> generically.
>
> Well, with defio being the hack it is (and because of that, a bunch of drm
> drivers not really supporting it) I'm not sure things actually work better
> without all this.
I don't understand what you mean.
What I do know is that fb_defio is here, and it's here to stay because some drivers need it.
What I also know is that I need to flush the screen after drawing my bootsplash.
>> What shall I do?
>>
>> Shall I add a new FB op for flushing when writing to the raw memory from the kernel?
>> As far as I can see, it would be needed for defio drivers only, is that correct?
>
> Yes, which are kinda horrible anyway. I guess you could at least not do
> all these hacks if it's not a defio driver.
Again, I don't understand.
In my patch (see below), I explicitly check for info->fbdefio, as well as three known broken drmfb emulations. I don't do the copy hack on any other device.
So, what shall I do? As it is, the hack is already specific to devices that really, really need it.
Would you like me to extend the FB API or not?
Max
> -Daniel
>
>>
>>
>>>> + *
>>>> + * A few DRM drivers' FB implementations are broken by not using
>>>> + * deferred_io when they really should - we match on the known
>>>> + * bad ones manually for now.
>>>> + */
>>>> + if (info->fbdefio
>>>> + || !strcmp(info->fix.id, "astdrmfb")
>>>> + || !strcmp(info->fix.id, "cirrusdrmfb")
>>>> + || !strcmp(info->fix.id, "mgadrmfb")) {
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next prev parent reply other threads:[~2017-12-19 13:34 UTC|newest]
Thread overview: 68+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-12-13 19:47 [RFC PATCH v2 00/13] Kernel based bootsplash Max Staudt
2017-12-13 19:47 ` [RFC PATCH v2 01/13] bootsplash: Initial implementation showing black screen Max Staudt
2017-12-13 23:55 ` Randy Dunlap
2017-12-14 15:37 ` Max Staudt
2017-12-13 19:47 ` [RFC PATCH v2 02/13] bootsplash: Add file reading and picture rendering Max Staudt
2017-12-13 19:47 ` [RFC PATCH v2 03/13] bootsplash: Flush framebuffer after drawing Max Staudt
2017-12-13 21:35 ` Daniel Vetter
2017-12-14 15:36 ` Max Staudt
2017-12-19 12:23 ` Daniel Vetter
2017-12-19 13:34 ` Max Staudt [this message]
2017-12-19 13:57 ` Daniel Vetter
2017-12-19 14:07 ` Oliver Neukum
2017-12-31 12:53 ` Alan Cox
2018-01-03 18:04 ` Max Staudt
2017-12-19 15:41 ` Max Staudt
2017-12-19 16:02 ` Daniel Vetter
2017-12-19 16:23 ` Max Staudt
2017-12-20 9:45 ` Daniel Vetter
2017-12-19 16:09 ` Daniel Vetter
2017-12-19 16:26 ` Max Staudt
2017-12-19 21:01 ` Ray Strode
2017-12-20 13:14 ` Max Staudt
2017-12-20 15:35 ` Ray Strode
2017-12-20 16:52 ` Max Staudt
2017-12-13 19:47 ` [RFC PATCH v2 04/13] bootsplash: Add corner positioning Max Staudt
2017-12-13 19:47 ` [RFC PATCH v2 05/13] bootsplash: Add animation support Max Staudt
2017-12-13 19:47 ` [RFC PATCH v2 06/13] vt: Redraw bootsplash fully on console_unblank Max Staudt
2017-12-13 19:47 ` [RFC PATCH v2 07/13] vt: Add keyboard hook to disable bootsplash Max Staudt
2017-12-13 19:47 ` [RFC PATCH v2 08/13] sysrq: Disable bootsplash on SAK Max Staudt
2017-12-13 19:47 ` [RFC PATCH v2 09/13] fbcon: Disable bootsplash on oops Max Staudt
2017-12-13 19:47 ` [RFC PATCH v2 10/13] Documentation: Add bootsplash main documentation Max Staudt
2017-12-13 19:47 ` [RFC PATCH v2 11/13] bootsplash: sysfs entries to load and unload files Max Staudt
2017-12-13 19:47 ` [RFC PATCH v2 12/13] tools/bootsplash: Add a basic splash file creation tool Max Staudt
2017-12-13 19:47 ` [RFC PATCH v2 13/13] tools/bootsplash: Add script and data to create sample file Max Staudt
2017-12-13 19:52 ` [RFC PATCH v2 00/13] Kernel based bootsplash Max Staudt
2017-12-19 16:16 ` Daniel Vetter
2017-12-19 17:04 ` Max Staudt
2017-12-19 17:26 ` Daniel Vetter
2017-12-19 18:40 ` Max Staudt
2017-12-20 9:43 ` Daniel Vetter
2017-12-20 10:06 ` Neil Armstrong
2017-12-20 10:14 ` Daniel Vetter
2017-12-20 14:55 ` Max Staudt
2017-12-20 15:11 ` Daniel Vetter
2017-12-20 15:19 ` Daniel Vetter
2017-12-20 15:22 ` Daniel Vetter
2017-12-20 16:23 ` Max Staudt
2017-12-20 16:15 ` Max Staudt
2017-12-31 12:44 ` Alan Cox
2018-01-03 18:00 ` Max Staudt
2017-12-20 14:16 ` Max Staudt
2017-12-20 14:10 ` Max Staudt
2017-12-31 12:35 ` Alan Cox
2018-01-03 17:56 ` Max Staudt
2017-12-19 20:30 ` Ray Strode
2017-12-20 13:03 ` Max Staudt
2017-12-20 15:21 ` Ray Strode
2017-12-20 16:44 ` Max Staudt
2017-12-21 14:51 ` Ray Strode
2017-12-21 16:32 ` Max Staudt
2017-12-20 11:08 ` Johannes Thumshirn
2017-12-20 11:22 ` Daniel Stone
2017-12-20 12:48 ` Johannes Thumshirn
2017-12-29 17:13 ` Jani Nikula
2018-01-03 17:38 ` Max Staudt
2017-12-21 9:48 ` Daniel Vetter
2017-12-21 16:52 ` Max Staudt
2017-12-21 15:00 ` Philip Müller
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