[PATCH 06/16] board: ti: Convert cape detection to use UCLASS framework

[Kory Maincent]

On Tue, 7 Oct 2025 08:11:48 -0600
Tom Rini <trini at konsulko.com> wrote:

> On Tue, Oct 07, 2025 at 11:32:13AM +0200, Kory Maincent wrote:
> > On Mon, 6 Oct 2025 17:42:40 -0600
> > Tom Rini <trini at konsulko.com> wrote:
> >   
> > > On Mon, Oct 06, 2025 at 05:30:15PM -0600, Simon Glass wrote:  
> > > > Hi Tom,
> > > > 
> > > > On Mon, 6 Oct 2025 at 15:44, Tom Rini <trini at konsulko.com> wrote:    
> > > > >
> > > > > On Mon, Oct 06, 2025 at 02:38:23PM -0600, Simon Glass wrote:    
> > > > > > Hi Kory,
> > > > > >
> > > > > > On Fri, 3 Oct 2025 at 10:34, Kory Maincent
> > > > > > <kory.maincent at bootlin.com> wrote:    
> > > > > > >
> > > > > > > Migrate TI board cape detection from legacy extension support to
> > > > > > > the new UCLASS-based extension board framework.
> > > > > > >
> > > > > > > Signed-off-by: Kory Maincent <kory.maincent at bootlin.com>  
> > 
> > ...
> >   
> > > > > > > -int extension_board_scan(struct list_head *extension_list)
> > > > > > > +static int ti_extension_board_scan(struct alist *extension_list)
> > > > > > >  {
> > > > > > >         unsigned char addr;
> > > > > > >         int num_capes = 0;
> > > > > > > @@ -31,7 +31,7 @@ int extension_board_scan(struct list_head
> > > > > > > *extension_list) struct am335x_cape_eeprom_id eeprom_header;
> > > > > > >                 char process_cape_part_number[17] = {'0'};
> > > > > > >                 char process_cape_version[5] = {'0'};
> > > > > > > -               struct extension *cape;
> > > > > > > +               struct extension cape = {0}, *_cape;
> > > > > > >                 struct udevice *dev;
> > > > > > >                 u8 cursor = 0;
> > > > > > >                 int ret, i;
> > > > > > > @@ -78,22 +78,20 @@ int extension_board_scan(struct list_head
> > > > > > > *extension_list)    
> > > > > >
> > > > > > I suppose that a method called scan() could be added to the uclass
> > > > > > and implemented by this driver.  
> > 
> > I don't understand what do you mean by method? Is it different to the
> > UBOOT driver scan ops I have designed? 
> >   
> > > > > > >                 printf("BeagleBone Cape: %s (0x%x)\n",
> > > > > > > eeprom_header.board_name, addr);
> > > > > > >
> > > > > > > -               cape = calloc(1, sizeof(struct extension));
> > > > > > > -               if (!cape) {
> > > > > > > -                       printf("Error in memory allocation\n");
> > > > > > > -                       return num_capes;
> > > > > > > -               }
> > > > > > > -
> > > > > > > -               snprintf(cape->overlay, sizeof(cape->overlay),
> > > > > > > "%s-%s.dtbo",
> > > > > > > +               snprintf(cape.overlay, sizeof(cape.overlay),
> > > > > > > "%s-%s.dtbo", process_cape_part_number, process_cape_version);
> > > > > > > -               strlcpy(cape->name, eeprom_header.board_name,
> > > > > > > +               strlcpy(cape.name, eeprom_header.board_name,
> > > > > > >                         sizeof(eeprom_header.board_name));
> > > > > > > -               strlcpy(cape->version, process_cape_version,
> > > > > > > +               strlcpy(cape.version, process_cape_version,
> > > > > > >                         sizeof(process_cape_version));
> > > > > > > -               strlcpy(cape->owner, eeprom_header.manufacturer,
> > > > > > > +               strlcpy(cape.owner, eeprom_header.manufacturer,
> > > > > > >                         sizeof(eeprom_header.manufacturer) + 1);
> > > > > > > -               list_add_tail(&cape->list, extension_list);
> > > > > > > +               _cape = alist_add(extension_list, cape);
> > > > > > > +               if (!_cape)
> > > > > > > +                       return -ENOMEM;
> > > > > > >                 num_capes++;
> > > > > > >         }
> > > > > > >         return num_capes;
> > > > > > >  }
> > > > > > > +
> > > > > > > +U_BOOT_EXTENSION(cape, ti_extension_board_scan);    
> > > > > >
> > > > > > Can the extension information go in the devicetree, so boards can
> > > > > > select their scheme that way?    
> > > > >
> > > > > Since we're scanning to see what extension boards are present and so
> > > > > what device tree overlays to apply, I don't think that can work?    
> > > > 
> > > > My understanding is that the scanning process is board-specific. For
> > > > example we would not want the Beagle mechanism to be compiled into
> > > > rpi. The idea of scanning things in a board-specific way seems like a
> > > > driver to me. Note there is also the SYSINFO uclass which can do
> > > > similar things.
> > > >
> > > > The overlays being applied here are additions to what should already
> > > > be a fairly complete devicetree.
> > > > 
> > > > If this isn't possible, then where is the information known?  
> > 
> > Oh, so you would prefer to have something like the sysinfo drivers.
> >    
> > > You're commenting on a patch to the TI specific code, that's only used
> > > by TI SoC using platforms that opt-in to the externally defined EEPROM
> > > format for these "capes". Perhaps your feedback would make more sense in
> > > some other part of the patch series? But even then, I'm not sure it
> > > makes sense?  
> > 
> > I am ok to move the cape scan detection code to a standalone driver with a
> > devicetree compatible match. Just wondering what are the advantages to use
> > standalone drivers instead of having the code in the specific board code as
> > done in this series.  
> 
> I'm not sure there is an advantage. Especially since in theory we could
> have more than one built in, and if ti_extension_board_scan(...) doesn't
> find anything (because the EEPROM is missing/wrong) we could still then
> call rpi_extension_board_scan(...) and look for that formatted type of
> EEPROM and then chipanddip_extension_board_scan(...) and look for that
> and so forth. These extensions are nominally discoverable and so don't
> need device tree compatibles, was some of the point of all this I would
> have sworn...

I think, he means a driver for each type of custom extension board scan
functions (4 until now). The U-boot devicetree would be like this:
extension_scan {
	compatible = "bone-cape-scan"; 
};

We could avoid the build of several extension drivers using Kconfig choice
symbol to select only one builtin.

On my side I don't really have opinions, it is a matter of code design. For now
I don't see real argument to tilt the balance except to do something like
sysinfo. We need more arguments from Simon.

Regards,
-- 
Köry Maincent, Bootlin
Embedded Linux and kernel engineering
https://bootlin.com