Re: [PATCH 1/7] Adding empia base driver

Hi Markus,

As promised I've done a review of your empia driver and looked at what
needs to be done to get it into the kernel.

First of all, I've no doubt that your empia driver is better and
supports more devices than the current em28xx driver. I also have no
problem adding your driver separate from the current driver. It's been
done before (certain networking drivers spring to mind) and while
obviously not ideal I expect that the older em28xx driver can probably
be removed after a year or something like that.

In my opinion it's pretty much hopeless trying to convert the current
em28xx driver into what you have. It's a huge amount of work that no
one wants to do and (in this case) with very little benefit. Of course,
Mauro has the final say in this.

While there is some cleaning up to do in your code (coding style, some
copyright/license clarifications), that is not a big deal. The coding
style cleanups are a fair amount of work, but I think we can probably
spread that out over several people and get that done quickly.

What I definitely would recommend is to use video_ioctl2 rather than
video_usercopy. The latter function will disappear in the future. I
think the policy for new drivers is to use video_ioctl2, so this is
probably a required task before it can be merged. Doing this will
improve maintenance of the code as well, so it's useful to do this
anyway. I think it's better if you do it, but I guess some volunteer
can probably be found if needed. It's not a difficult task.

Now the real problems are with three duplicate i2c drivers: cx25843,
xc3028 and xc5000.

To start with the easiest one: cx25843. There already is a driver for
this (cx25840) and the empia driver should use that one. Since I
maintain cx25840 the easiest approach for you is to see if you can get
me hardware (em28xx + cx25843) so that I can test and update cx25843 to
provide proper empia support. The alternative is that we work together
on this, but that's probably more work for both of us. I most
definitely do *not* want to duplicate this driver. Windows drivers
duplicate this stuff all the time, but we're not Windows and having one
driver ensures that fixes or new functionality become available to all
bridge drivers that use it.

The same reasoning is true for xc3028 and xc5000. In addition, the
licensing of these sources is very vague. Is it even allowed to
distribute them under a GPL license? There is no GPL license in the
sources, yet in the module you specify GPL. This needs to be clarified
first.

I see two ways forward when it comes to these drivers:

1) The empia driver switches to the current xceive drivers that are
already in the kernel. No doubt this means that xceive driver bugs will
surface with certain devices, but those are bugs that the xceive driver
maintainer will have to fix. Obviously assistance would be appreciated,
but the bottom line is that a) your driver is finally in the kernel,
and b) there is a lot more pressure to fix bugs in the xceive drivers
than is the case otherwise. Yes, some devices will not work initially
with the empia driver, but I expect that to be a temporary situation.

2) Your xceive drivers replace the current drivers. This will require
that a) the license situation is clarified, b) the drivers are modified
to fit the current v4l-dvb tuner architecture. This option will mean a
lot of work for you since you are the maintainer of these drivers. In
addition, I forsee a lot of flaming if we go this way.

BTW, I noticed that the current xc5000 driver is very similar to yours
but with proper copyrights/license notices and coding style. So for
this driver option 1 is definitely the way to go.

To be honest, I don't see option 2 as viable. I forsee too many
inter-personal problems that will appear if we go that way. Option 1
has the big advantage that all you need to do is to file a bug report
if it doesn't work with a certain device. And in the meantime users can
fallback to your stand-alone driver until it's fixed in the kernel.
Obviously, if you can state in the bug report what the precise problem
is, so much the better.

So my recommendation would be to:

1) Switch to using the current xceive drivers in your empia driver. This
is something you have to do, I'm afraid. Unless someone would
volunteer? I personally do not have enough experience with this to do
it.

2) Switch to using the cx25840 driver. If I can get hardware, then I can
do this, otherwise we have to do this together. Initially we probably
have to disable devices using the cx25840 until the cx25840 driver has
been fixed for the empia driver.

3) Switch to video_ioctl2 in the empia driver. You can do that, but we
can probably find a volunteer as well.

4) Conform the code to the coding style. If several people can help with
this we can get it done pretty quickly.

5) Merge the empia driver alongside the current em28xx driver.

There are no doubt some things I missed, but I don't think I missed
anything major. I've put up a hg tree here:

[url]http://linuxtv.org/hg/~hverkuil/v4l-dvb-em28xx/[/url]

This allows you to compile the empia module alongside the em28xx module.
Note that I've removed the empia cx25843 module in the last changeset
in order to test which dependencies the driver had on that module. So
if you want to test this tree with an empia+cx25843 device, then don't
get the latest changeset, but the one before that.

My tree does contain the empia xceive drivers, though. Perhaps someone
more knowledgeable with DVB can take a look to see how much work it is
to convert to the kernel xceive drivers? And to see if I overlooked any
DVB-related major obstacles?

I think this is a reasonable roadmap to finally get this in. If everyone
can pitch in then it really shouldn't take that much work to get it
into v4l-dvb and from there to 2.6.29.

Regards,

Hans Verkuil
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On Sat, 1 Nov 2008 14:59:17 +0100
Hans Verkuil <hverkuil@xs4all.nl> wrote:
[color=blue]
> Hi Markus,
>
> As promised I've done a review of your empia driver and looked at what
> needs to be done to get it into the kernel.
>
> First of all, I've no doubt that your empia driver is better and
> supports more devices than the current em28xx driver. I also have no
> problem adding your driver separate from the current driver. It's been
> done before (certain networking drivers spring to mind) and while
> obviously not ideal I expect that the older em28xx driver can probably
> be removed after a year or something like that.
>
> In my opinion it's pretty much hopeless trying to convert the current
> em28xx driver into what you have. It's a huge amount of work that no
> one wants to do and (in this case) with very little benefit. Of course,
> Mauro has the final say in this.
>[/color]

Both upstream and the 4 duplicated drivers have similar functionality. Also,
the upstream driver is actively maintained. So, there's no sense on accepting
those duplicated drivers.

Also, just replacing one existing driver by a newer one will cause regressions
on some already fixed bugs and remove some improvements that the upstream driver
suffered.

If there's a bug or a lack of functionality on em28xx, cx25843, xc5000 or
tuner-xc2028, it is just a matter of submitting patches fixing those bugs or
adding newer features.

Cheers,
Mauro
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On Sat, 8 Nov 2008 03:50:20 -0200
"Andre Kelmanson" <akelmanson@gmail.com> wrote:
[color=blue]
> Dears,
>
> I'm using this version of em28xx for a long time and it's working fine. It
> has three very important features for me. The first one is Kaiomy device,
> the second one is the new em28xx-audoep module and the third one is PAL-M
> support. Kaiomy and PAL-M support were developed based on my support on the
> em28xx mailinglist.
>
> Now I can use my device (Kaiomy) outside Windows with sound (em28xx-audioep)
> and colors (PAL-M)! I'm using this version everyday with no problems.
>
> Because of this, it will be nice if this work could be included in the
> kernel code. What do you (other users) think about having that driver in
> kernel?[/color]

André,

First of all, the big issue why we aren't merging em28xx improvements from
Markus is that he is not following the rules.

For example, you said that you've contributed with Markus tree.

However, on Markus pull request, I see no patch from you on his series of patches.

The correct procedure would be just to forward your patch as-is, adding with his SOB bellow yours.

Not doing this, he would be considered as the author of your patch. IANAL, but
this doesn't seem to be right, from GPL's perspective. Probably, there are
other patches there not authored by Markus that are just merged inside his big patch.

About PAL-M, this always worked at the upstream driver. I have myself lots of
em28xx devices, all working in colors with PAL-M, and with audio. I live in
Brazil, so I always check if PAL-M is ok ;)

If you want to have your device supported, just send us a patch against the
upstream driver.

Cheers,
Mauro
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On Sat, Nov 8, 2008 at 11:15 AM, Mauro Carvalho Chehab
<mchehab@infradead.org> wrote:[color=blue]
> On Sat, 8 Nov 2008 03:50:20 -0200
> "Andre Kelmanson" <akelmanson@gmail.com> wrote:
>[color=green]
>> Dears,
>>
>> I'm using this version of em28xx for a long time and it's working fine. It
>> has three very important features for me. The first one is Kaiomy device,
>> the second one is the new em28xx-audoep module and the third one is PAL-M
>> support. Kaiomy and PAL-M support were developed based on my support on the
>> em28xx mailinglist.
>>
>> Now I can use my device (Kaiomy) outside Windows with sound (em28xx-audioep)
>> and colors (PAL-M)! I'm using this version everyday with no problems.
>>
>> Because of this, it will be nice if this work could be included in the
>> kernel code. What do you (other users) think about having that driver in
>> kernel?[/color]
>
> André,
>
> First of all, the big issue why we aren't merging em28xx improvements from
> Markus is that he is not following the rules.
>
> For example, you said that you've contributed with Markus tree.
>
> However, on Markus pull request, I see no patch from you on his series of patches.
>
> The correct procedure would be just to forward your patch as-is, adding with his SOB bellow yours.
>
> Not doing this, he would be considered as the author of your patch. IANAL, but
> this doesn't seem to be right, from GPL's perspective. Probably, there are
> other patches there not authored by Markus that are just merged inside his big patch.
>
> About PAL-M, this always worked at the upstream driver. I have myself lots of
> em28xx devices, all working in colors with PAL-M, and with audio. I live in
> Brazil, so I always check if PAL-M is ok ;)
>
> If you want to have your device supported, just send us a patch against the
> upstream driver.
>[/color]

As written earlier already I don't think that I didn't follow any
rules here since I provided single
patches at the very first beginning

[url]http://mcentral.de/v4l-dvb/[/url]
(this is all kernel code and only kernel code).

That work didn't get attention and due a different decision of
framework changes (which that codebase relied
on) it all had to be rebased, I doubt that anyone
would have reworked all that patch for patch. Instead it went into one
repository and finally got modified to work again
with the available framework rather than relying onto any such modifications.

The modification which I received from André suggested to use the NTSC
VBI offset lines for PAL-M, and the
rest for audio comes from my side.

Markus
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On Sat, 8 Nov 2008, Markus Rechberger wrote:
[color=blue]
> As written earlier already I don't think that I didn't follow any
> rules here since I provided single
> patches at the very first beginning
>
> [url]http://mcentral.de/v4l-dvb/[/url]
> (this is all kernel code and only kernel code).
>
> That work didn't get attention and due a different decision of
> framework changes (which that codebase relied
> on) it all had to be rebased, I doubt that anyone
> would have reworked all that patch for patch. Instead it went into one
> repository and finally got modified to work again
> with the available framework rather than relying onto any such modifications.[/color]

One thing is to rebase a tree, another is to merge all patches into a big
one, not preserving the original authorships.

Development trees sometimes need rebase. This is done by popping all newer
patches from the tree, applying the upstream patches, and then pushing
again every individual patches, fixing the ones that don't apply well, but
preserving their authorships.

The modified patches should receive a special tag before the
maintainer's SOB, like:

[me@mymail: I did this to apply this patch]

as stated at the kernel docs.

This method will reduce a lot the risk of breaking improvements and other
fixes that happened upstream, and will properly preserve authorship of
individual patches.

If you were doing a rebase, your patches would likely be accepted.

--
Cheers,
Mauro
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On Sat, Nov 8, 2008 at 11:42 AM, Markus Rechberger
<mrechberger@gmail.com> wrote:[color=blue]
> On Sat, Nov 8, 2008 at 11:37 AM, Mauro Carvalho Chehab
> <mchehab@infradead.org> wrote:[color=green]
>> On Sat, 8 Nov 2008, Markus Rechberger wrote:
>>[color=darkred]
>>> As written earlier already I don't think that I didn't follow any
>>> rules here since I provided single
>>> patches at the very first beginning
>>>
>>> [url]http://mcentral.de/v4l-dvb/[/url]
>>> (this is all kernel code and only kernel code).
>>>
>>> That work didn't get attention and due a different decision of
>>> framework changes (which that codebase relied
>>> on) it all had to be rebased, I doubt that anyone
>>> would have reworked all that patch for patch. Instead it went into one
>>> repository and finally got modified to work again
>>> with the available framework rather than relying onto any such
>>> modifications.[/color]
>>
>> One thing is to rebase a tree, another is to merge all patches into a big
>> one, not preserving the original authorships.
>>
>> Development trees sometimes need rebase. This is done by popping all newer
>> patches from the tree, applying the upstream patches, and then pushing again
>> every individual patches, fixing the ones that don't apply well, but
>> preserving their authorships.
>>
>> The modified patches should receive a special tag before the maintainer's
>> SOB, like:
>>
>> [me@mymail: I did this to apply this patch]
>>
>> as stated at the kernel docs.
>>
>> This method will reduce a lot the risk of breaking improvements and other
>> fixes that happened upstream, and will properly preserve authorship of
>> individual patches.
>>
>> If you were doing a rebase, your patches would likely be accepted.
>>[/color]
>[/color]

let's link back to the only review done:
[url]http://linux.derkeiler.com/Mailing-Lists/Kernel/2008-11/msg00060.html[/url]

<snip>
In my opinion it's pretty much hopeless trying to convert the current
em28xx driver into what you have. It's a huge amount of work that no
one wants to do and (in this case) with very little benefit.
</snip>

Markus
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On Sat, Nov 8, 2008 at 11:37 AM, Mauro Carvalho Chehab
<mchehab@infradead.org> wrote:[color=blue]
> On Sat, 8 Nov 2008, Markus Rechberger wrote:
>[color=green]
>> As written earlier already I don't think that I didn't follow any
>> rules here since I provided single
>> patches at the very first beginning
>>
>> [url]http://mcentral.de/v4l-dvb/[/url]
>> (this is all kernel code and only kernel code).
>>
>> That work didn't get attention and due a different decision of
>> framework changes (which that codebase relied
>> on) it all had to be rebased, I doubt that anyone
>> would have reworked all that patch for patch. Instead it went into one
>> repository and finally got modified to work again
>> with the available framework rather than relying onto any such
>> modifications.[/color]
>
> One thing is to rebase a tree, another is to merge all patches into a big
> one, not preserving the original authorships.
>
> Development trees sometimes need rebase. This is done by popping all newer
> patches from the tree, applying the upstream patches, and then pushing again
> every individual patches, fixing the ones that don't apply well, but
> preserving their authorships.
>
> The modified patches should receive a special tag before the maintainer's
> SOB, like:
>
> [me@mymail: I did this to apply this patch]
>
> as stated at the kernel docs.
>
> This method will reduce a lot the risk of breaking improvements and other
> fixes that happened upstream, and will properly preserve authorship of
> individual patches.
>
> If you were doing a rebase, your patches would likely be accepted.
>[/color]

Should I start picking patches from the linuxtv.org tree where patches
from my tree are taken
and where the Sign off is not provided?

Just recently one patch went into not even stating that it comes from
my codebase, although not
worth the time making an elephant out of it.

Markus
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On Sat, 8 Nov 2008, Markus Rechberger wrote:
[color=blue]
> Should I start picking patches from the linuxtv.org tree where patches
> from my tree are taken
> and where the Sign off is not provided?[/color]

SOB's are just meant to testify that the code is GPL. It has nothing to do
with authorship.

On all cases I'm aware, when some code from your tree were merged
upstream, your authorship were marked inside the patch's description.
Also, your authorship are explicit at the em28xx files you've contributed.

--
Cheers,
Mauro Carvalho Chehab
[url]http://linuxtv.org[/url]
[email]mchehab@infradead.org[/email]
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On Sat, Nov 8, 2008 at 11:56 AM, Mauro Carvalho Chehab
<mchehab@infradead.org> wrote:[color=blue]
> On Sat, 8 Nov 2008, Markus Rechberger wrote:
>[color=green]
>> Should I start picking patches from the linuxtv.org tree where patches
>> from my tree are taken
>> and where the Sign off is not provided?[/color]
>
> SOB's are just meant to testify that the code is GPL. It has nothing to do
> with authorship.
>
> On all cases I'm aware, when some code from your tree were merged upstream,
> your authorship were marked inside the patch's description. Also, your
> authorship are explicit at the em28xx files you've contributed.
>[/color]

really?
[url]http://linuxtv.org/hg/v4l-dvb/rev/5f3c3af9c1f9[/url]

[url]http://article.gmane.org/gmane.linux.drivers.dvb/44726[/url]

nevermind.

Markus
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