Re: [PATCH v12 1/1] mux: Add driver for Renesas RZ/V2H USB VBENCTL VBUS_SEL mux

[Peter Rosin]

On 2026-08-07 12:05, Tommaso Merciai wrote:
> On Fri, Aug 07, 2026 at 08:23:13AM +0200, Peter Rosin wrote:
>> I'm not previously familiar with the auxiliary bus. When I read about
>> it I find this:
>>
>> 	"A key requirement for utilizing the auxiliary bus is that
>> 	there is no dependency on a physical bus, device, register
>> 	accesses or regmap support."
>>
>> That seems to contradict this driver with its dependency on regmap,
>> thus violating the above key requirement?
> 
> I'm seeing a very close pattern in [1]. clk-imx8ulp-sim-lpav.c create a
> regmap for its auxiliary reset and mux driver. 
> 
> The parent driver is creating the axuiliary device in [2], this create
> "clk_imx8ulp_sim_lpav.reset".
> 
> Then later reset-imx8mp-audiomix.c into
> imx8mp_audiomix_reset_get_regmap() [3] take the rgmap from the parent.
> 
> Also reset-meson-aux.c [4] is aux device and is taking the regmap
> from the parent.
> 
> IMHO the doc paragraph share why such a device can't be a platform
> device or an MFD, matching on the auxiliary bus is a plain
> string compare, so no register access is involved in match or bind.
> 
> [1] https://elixir.bootlin.com/linux/v7.2-rc6/source/drivers/clk/imx/clk-imx8ulp-sim-lpav.c#L95
> [2] https://elixir.bootlin.com/linux/v7.2-rc6/source/drivers/clk/imx/clk-imx8ulp-sim-lpav.c#L123
> [3] https://elixir.bootlin.com/linux/v7.2-rc6/source/drivers/reset/reset-imx8mp-audiomix.c#L162
> [4] https://elixir.bootlin.com/linux/v7.2-rc6/source/drivers/reset/amlogic/reset-meson-aux.c#L65
Yes, agreed, regmap usage from the aux bus seem pretty widespread, and
not being allowed to touch regmap would be quite odd...

Looking forward to v13, thanks!

Cheers,
Peter