[alsa-devel] [PATCH 1/2] ucm: Automatically load the best config file based on the card long name

[Liam Girdwood]

On Fri, 2016-12-23 at 16:08 +0800, Mengdong Lin wrote:
> On 12/22/2016 11:35 PM, Liam Girdwood wrote:
> 
> >>>>>> +/* This function will find the best device-specific configuration
> >>>>>> +file based
> >>>>>> + * on the sound card long name.
> >>>>>> + * Different devices may share the same sound driver and thus the
> >>>>>> +same sound
> >>>>>> + * card name (short name), but they may still need different
> >>>>>> +device-specific
> >>>>>> + * configurations. For user space to differentiate them, kernel
> >>>>>> +drivers may
> >>>>>> + * include the DMI info (vendor, product and board) in the card
> >>>>>> +long
> >>>>> name.
> >>>>>> + * And user space can define configuration file names appending
> >>>>>> +DMI keywords
> >>>>>> + * to the card name, like:
> >>>>>> + * bytcr-rt5640.ASUS.T100
> >>>>>> + * bytcr-rt5651.MinnowBoard
> >>>>>> + *
> >>>>>> + * When being asked to load the configuration file for a card,
> >>>>>> +this function
> >>>>>> + * will try to find the card long name from the local machine,
> >>>>>> +and then scan
> >>>>>> + * all available configuration file names, search every field of
> >>>>>> +the config
> >>>>>> + * file name in the card long name. The more characters match,
> >>>>>> +the higher
> >>>>>> + * score the file has. Finally, the file with the highest score will be
> >>> loaded.
> >>>>>> + */
> >>>>>
> >>>>> Id' expect this function to try and open card longname and then card
> >>>>> name if longname is not found. So providing we use the exact same
> >>>>> names as the DMI name we wont need any string formatting or scoring
> >>>>> (i.e. file
> >>>>> open("longname/longname.conf") will either succeed or fail)
> >>>>>
> >>>>> Liam
> >>>>
> >>>> I feel we cannot use the exact same names for the configuration file
> >>>> and card long name. The DMI info in the card long name can be lengthy,
> >>>> including '.' , SPACE, meaningless info like "Corp." and sometime
> >>>> duplicated info for some OEMs．I hope developers can just extract key
> >>>> words from the messy DMI info to make a simple configuration file
> >>>> name, and UCM automatically do the matching and give each
> >>>> configuration file a score. Then the file with highest score will be
> >>>> used for the card.
> >>>
> >>> Providing the DMI name does not use invalid filename characters we are ok.
> >>> Extracting key words and matching is prone to many problems and painful to
> >>> debug....
> >>
> >> May I revise the UCM code like this? It will try to open the file with
> >> DMI name at first. And only if that file is not available, fall back
> >> to key words matching.
> >>
> >> I hope to keep the possibility that user can use a simple
> >> configuration file for a product family, without generating too many
> >> card directories and files.
> >>
> >
> > If the DMI names are too complex for directory names, then you could add
> > an alias file at the top level that would list the DMI name and the
> > shortened name i.e.
> >
> > # DMI name                     # UCM directory name
> > "Dell blah Corp. XPS, 13 blah" "Dell XPS13 BDW"
> >
> > So the alias file could be searched for the DMI name, before the legacy
> > name was tried.
> >
> > The alias method above also allows for reuse of configs on machines that
> > are similar, but with different DMI names. So this would also keep the
> > number of configs low.
> >
> > Liam
> 
> I'll try to use the alias file. But it seems we need to maintain a lot 
> of entries in the file :-(
> 
> In addition, I found we cannot use paths with SPACE as the UCM directory 
> name. Autoconf cannot support this. It complains although I tried \ or " 
> to escape. We need something like "Dell.XPS13.BDW" as the UCM directory 
> names.
> 

Gah, it looks like autoconf may have defeated this ! Autoconf has
special uses for some chars in names.

So you may want to "fix" the DMI name to exclude any special chars when
creating your longname (maybe also set a shorter length too). I still
dont want any scoring, we just want to open the "longname.conf" then
"drivername.conf"

Liam