[alsa-devel] A few general questions (my first driver): Marian MARC4

[Takashi Iwai]

At Fri, 20 Jun 2008 02:07:49 -0400,
Joshua Boyd wrote:
> 
> I have a Marian Marc4 card.  I have the documentation for this card,  
> which has been on their web site for quite some time.  I want to  
> write a driver for this card.  This is my first ALSA driver, but it  
> isn't my first kernel driver.
> 
> Anyway, I can't google any mention of this family of cards on this  
> mailing list, which seems a bit odd.  I did find some mentions on  
> linux-audio-developer, about the documentation, but no mention there  
> of prior work on this family.
> 
> However, I did find a MARC8 driver on sourceforge (http:// 
> sourceforge.net/projects/marc8-driver).  Does anyone know anything  
> about this?  I'm vary curious about why I've never seen it mentioned  
> here before.  The license is listed as GPL.  The Marian Marc8 was  
> formerly known as the Sek'd Siena, but again I can't find any real  
> mention of that in the archives.  Does anyone have any idea why the  
> MARC8 wasn't mentioned and merged into the main ALSA sources?

AFAIK, no one suggested or posted the patches to ALSA developers.
So it's a totally unknown project.

> I did go ahead and add some Marian product information to the support  
> matrix on the alsa wiki, including a link to the sourceforge page.
> 
> My plan is to add MARC4 to the MARC8 driver.  The register layout is  
> basically the same, adjusted for the 4 versus 8 channels.  Both cards  
> use the same PLX chip.  The biggest difference is in the layout of  
> the play/capture RAM area, which is because of the 4 versus 8  
> channels.  It seems silly to make two separate drivers.  I would like  
> to see my results eventually merged into the main ALSA.  I'm hoping  
> that if I get these into the main tree that I would then be able to  
> get some support from Marian in the form of clearance (and a card) to  
> do the Trace D4 and D4 SRC, and possibly even documentation and  
> hardware for the UCON CX.
> 
> Anyway, moving on to my specific questions.
> 
> First, is it appropriate to put support for two device IDs in the  
> same file?  The examples I tried looking at ended up being a single  
> device id, differentiated by a subvendor ID.

It's no problem.

> Second, is it wrong to use the same structures, but with an enum  
> field in the main snd_marc device structure that points out which  
> card I'm talking about, then else where switching on that enum to  
> figure out how many channels I need to operate on?

Nothing wrong.  Passing driver_data in pci_device_id table is a common
technique.

> Third, once I get this functional on my MARC4 card, how hard is it  
> likely to be to get it accepted?  I don't expect low standards for  
> code that is accepted, but I'd like to have some idea how picky the  
> process may be.

This really depends on the code quality.  Of course, the most
important criteria is that the driver works without problems, though
:)

Anyway, a good hint can be found in Documentation/CodingStyle in
linux kernel tree.  At least, check $LINUX/scripts/checkpatch.pl
before submitting your patch.


thanks,

Takashi