linux-kernel - Re: [PATCH 2/2] soundwire: bus: Allow SoundWire peripherals to register IRQ handlers

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Date:   Fri, 20 Jan 2023 09:59:41 +0000
From:   Charles Keepax <ckeepax@...nsource.cirrus.com>
To:     Pierre-Louis Bossart <pierre-louis.bossart@...ux.intel.com>
CC:     <vkoul@...nel.org>, <yung-chuan.liao@...ux.intel.com>,
        <sanyog.r.kale@...el.com>, <alsa-devel@...a-project.org>,
        <linux-kernel@...r.kernel.org>, <patches@...nsource.cirrus.com>
Subject: Re: [PATCH 2/2] soundwire: bus: Allow SoundWire peripherals to
 register IRQ handlers

On Thu, Jan 19, 2023 at 11:12:04AM -0600, Pierre-Louis Bossart wrote:
> No objection on this addition, just a couple of comments to improve it:
> 
> >  EXPORT_SYMBOL(sdw_bus_master_add);
> > @@ -158,6 +183,8 @@ static int sdw_delete_slave(struct device *dev, void *data)
> >  	mutex_lock(&bus->bus_lock);
> >  
> >  	if (slave->dev_num) { /* clear dev_num if assigned */
> > +		irq_dispose_mapping(irq_find_mapping(bus->domain, slave->dev_num));
> > +
> 
> could this be done conditionally. e.g.
> 
> if (slave->prop.irq)
>     irq_dispose_mapping(irq_find_mapping(bus->domain, slave->dev_num));
> 
> > +			slave->irq = irq_create_mapping(bus->domain, dev_num);
> > +			if (!slave->irq) {
> > +				dev_err(bus->dev, "Failed to map IRQ\n");
> > +				return -EINVAL;
> > +			}
> 
> ...and here....
> 
> if (slave->prop.irq) {
> 	slave->irq = irq_create_mapping(bus->domain, dev_num);
> 	if (!slave->irq) {
> 		dev_err(bus->dev, "Failed to map IRQ\n");
> 		return -EINVAL;
> 	}
> }
> 

Yeah I am happy to make those conditional, I guess it is cleaner
to not map IRQs if they wont be used.

> > @@ -369,6 +371,7 @@ struct sdw_dpn_prop {
> >   * @clock_reg_supported: the Peripheral implements the clock base and scale
> >   * registers introduced with the SoundWire 1.2 specification. SDCA devices
> >   * do not need to set this boolean property as the registers are required.
> > + * @irq: call actual IRQ handler on slave, as well as callback
> >   */
> >  struct sdw_slave_prop {
> >  	u32 mipi_revision;
> > @@ -393,6 +396,7 @@ struct sdw_slave_prop {
> >  	u8 scp_int1_mask;
> >  	u32 quirks;
> >  	bool clock_reg_supported;
> > +	bool irq;
> 
> this can be confused with the 'wake_capable' property.
> 
> maybe 'out_of_band_irq' ?
> 

Yes I struggle on the name a bit and then just gave up and
went with plain "irq", hard to know what to call it. Not sure
out_of_band is quite right since it not really out of band,
handle_nested_irq pretty much basically boils down to a function
call really. Maybe something like "map_irq", or "use_domain_irq"?

> There should be an explanation and something checking that both are not
> used concurrently.

I will try to expand the explanation a litte, but I dont see any
reason to block calling both handlers, no ill effects would come
for a driver having both and it is useful if any soundwire
specific steps are needed that arn't on other control buses.

Thanks,
Charles