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

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Message-ID: <d6bd466a5d11b016183db0ac3c25185fad3036fc.camel@gmail.com>
Date: Fri, 17 Oct 2025 15:25:42 +0200
From: Alexander Sverdlin <alexander.sverdlin@...il.com>
To: Herve Codina <herve.codina@...tlin.com>
Cc: David Rhodes <david.rhodes@...rus.com>, Richard Fitzgerald	
 <rf@...nsource.cirrus.com>, Liam Girdwood <lgirdwood@...il.com>, Mark Brown
	 <broonie@...nel.org>, Rob Herring <robh@...nel.org>, Krzysztof Kozlowski	
 <krzk+dt@...nel.org>, Conor Dooley <conor+dt@...nel.org>, Jaroslav Kysela	
 <perex@...ex.cz>, Takashi Iwai <tiwai@...e.com>, Nikita Shubin	
 <nikita.shubin@...uefel.me>, Axel Lin <axel.lin@...ics.com>, Brian Austin	
 <brian.austin@...rus.com>, linux-sound@...r.kernel.org, 
	patches@...nsource.cirrus.com, devicetree@...r.kernel.org, 
	linux-kernel@...r.kernel.org, Thomas Petazzoni
 <thomas.petazzoni@...tlin.com>
Subject: Re: [PATCH 1/3] ASoC: cs4271: Fix cs4271 I2C and SPI drivers
 automatic module loading

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@...30000/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@...a0000/codec@0
OF_COMPATIBLE_0=cirrus,cs4271
OF_COMPATIBLE_N=1
MODALIAS=spi:cs4271

> > 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.

> --- 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@...dex.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< ---

-- 
Alexander Sverdlin.