Re: [PATCH 1/3] ASoC: cs4271: Fix cs4271 I2C and SPI drivers automatic module loading

[Herve Codina <herve.codina@bootlin.com>]

Hi Alexander,

On Fri, 17 Oct 2025 15:25:42 +0200
Alexander Sverdlin <alexander.sverdlin@gmail.com> wrote:

> Hi Herve,
> 
> On Fri, 2025-10-17 at 08:32 +0200, Herve Codina wrote:
> > ...
> >   
> > > > In order to have the I2C or the SPI module loaded automatically, move
> > > > the MODULE_DEVICE_TABLE(of, ...) the core to I2C and SPI parts.
> > > > Also move cs4271_dt_ids itself from the core part to I2C and SPI parts
> > > > as both the call to MODULE_DEVICE_TABLE(of, ...) and the cs4271_dt_ids
> > > > table itself need to be in the same file.    
> > > 
> > > I'm a bit confused by this change.
> > > What do you have in SYSFS "uevent" entry for the real device?  
> > 
> > Here is my uevent content:
> > --- 8<---
> > # cat /sys/bus/i2c/devices/3-0010/uevent 
> > DRIVER=cs4271
> > OF_NAME=cs4271
> > OF_FULLNAME=/i2c@ff130000/cs4271@10
> > OF_COMPATIBLE_0=cirrus,cs4271
> > OF_COMPATIBLE_N=1
> > MODALIAS=of:Ncs4271T(null)Ccirrus,cs4271
> > # 
> > --- 8< ---  
> 
> that's what I get with SPI-connected CS4271, and this is actually what I'd
> expect (linux-next as of 2433b8476165):
> 
> # cat /sys/bus/spi/devices/spi0.0/uevent
> DRIVER=cs4271
> OF_NAME=codec
> OF_FULLNAME=/soc/spi@808a0000/codec@0
> OF_COMPATIBLE_0=cirrus,cs4271
> OF_COMPATIBLE_N=1
> MODALIAS=spi:cs4271

So, this is without my patch applied.
I don't have any CS4271 connected on SPI bus to perform the same test
with my patch applied.

> 
> > > If you consider spi_uevent() and i2c_device_uevent(), "MODALIAS=" in the
> > > "uevent" should be prefixed with either "spi:" or "i2c:".
> > > And this isn't what you adress in your patch.
> > > 
> > > You provide [identical] "of:" prefixed modalias to two different modules
> > > (not sure, how this should work), but cs4271 is not an MMIO device,
> > > so it should not generate an "of:" prefixed uevent.
> > > 
> > > Could you please show the relevant DT snippet for the affected HW?  
> > 
> > And this is the related DT part:
> > --- 8< ---
> > &i2c3 {
> >  status = "okay";
> > 
> >  cs4271@10 {
> >  compatible = "cirrus,cs4271";
> >  reg = <0x10>;
> >  clocks = <&cru SCLK_I2S_8CH_OUT>;
> >  clock-names = "mclk";
> > 
> >  ...
> >  };
> > };
> > --- 8< ---
> > 
> > i2c3 is the following node:
> > https://elixir.bootlin.com/linux/v6.17.1/source/arch/arm64/boot/dts/rockchip/rk3399-base.dtsi#L732  
> 
> the above looks OK to me on the first glance, I'm really puzzled what
> is the reason for "of:" prefixed MODALIAS in the uevent for an i2c device.
> 
> I still believe, that the culprit is the creation of a platform device
> from the DT for an i2c device.
> 
> I don't have any real I2C-connected CS4271, but I think I could fake one
> in any DT just to verify how uevents would look like on my side.
> 
> > About the related module, I have the following:  
> 
> I assume, this is with your patch applied though.

Yes, exactly.

> 
> > --- 8< ---
> > # modinfo snd_soc_cs4271_i2c
> > filename:       /lib/modules/6.18.0-rc1xxxx-00050-g4fa36970abe5-dirty/kernel/sound/soc/codecs/snd-soc-cs4271-i2c.ko
> > license:        GPL
> > author:         Alexander Sverdlin <subaparts@yandex.ru>
> > description:    ASoC CS4271 I2C Driver
> > alias:          i2c:cs4271
> > alias:          of:N*T*Ccirrus,cs4271C*
> > alias:          of:N*T*Ccirrus,cs4271
> > depends:        snd-soc-cs4271
> > intree:         Y
> > name:           snd_soc_cs4271_i2c
> > vermagic:       6.18.0-rc1xxxx-00050-g4fa36970abe5-dirty SMP preempt mod_unload aarch64
> > # 
> > --- 8< ---  
> 

Best regards,
Hervé