linux-kernel - Re: [PATCH v2 3/4] dt-bindings: i2c-stm32: add SMBus Alert bindings

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Date:   Mon, 13 Jul 2020 20:30:48 -0600
From:   Rob Herring <robh@...nel.org>
To:     Wolfram Sang <wsa@...nel.org>
Cc:     Alain Volmat <alain.volmat@...com>, mark.rutland@....com,
        pierre-yves.mordret@...com, mcoquelin.stm32@...il.com,
        alexandre.torgue@...com, linux-i2c@...r.kernel.org,
        devicetree@...r.kernel.org,
        linux-stm32@...md-mailman.stormreply.com,
        linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
        fabrice.gasnier@...com
Subject: Re: [PATCH v2 3/4] dt-bindings: i2c-stm32: add SMBus Alert bindings

On Tue, Jun 30, 2020 at 09:41:07PM +0200, Wolfram Sang wrote:
> On Thu, Jun 25, 2020 at 09:39:28AM +0200, Alain Volmat wrote:
> > Add a new binding of the i2c-stm32f7 driver to enable the handling
> > of the SMBUS-Alert.
> > 
> > The I2C/SMBUS framework already provides a mechanism to enable SMBus-Alert
> > by naming an IRQ line "smbus_alert". However, on stm32, the SMBus-Alert is
> > part of the i2c IRQ. Using the smbus_alert naming here would lead to having
> > 2 handlers (the handler of the driver and the smbus_alert handler
> > from I2C/SMBUS framework) on the unique i2c IRQ of the stm32. Meaning that
> > the smbus_alert handler would get called for all IRQ generated by the stm32
> > I2C controller.
> > 
> > For that reason, the smbus_alert IRQ naming cannot be used and a dedicated
> > binding is introduced.
> 
> What if we update the core to not register another irq handler if the
> "smbus_alert" and main irq are the same?
> 
> I think it could work. However, while trying to make a proof-of-concept,
> I found that irq descriptions in the generic i2c binding document are
> probably mixed up. And before fixing that, I'd like to get HostNotify
> done first.

Why does this even need to be in DT? Can't the driver just register that 
it supports SMBus alert or have some call to the core signaling an SMBus 
alert? 

Rob