Re: [PATCH] i2c: i801: Register optional lis3lv02d i2c device on Dell machines

[Dmitry Torokhov]

On Wed, Jan 04, 2017 at 06:46:19PM +0100, Wolfram Sang wrote:
> 
> > How about:
> > ---
> > From daa7571bbf337704332c0cfeec9b8fd5aeae596f Mon Sep 17 00:00:00 2001
> > From: Benjamin Tissoires <benjamin.tissoires@xxxxxxxxxx>
> > Date: Wed, 4 Jan 2017 18:26:54 +0100
> > Subject: [PATCH] I2C: add the source of the IRQ in struct i2c_client
> > 
> > With commit 4d5538f5882a ("i2c: use an IRQ to report Host Notify events,
> > not alert"), the IRQ provided in struct i2c_client might be assigned while
> > it has not been explicitly declared by either the platform information
> > or OF or ACPI.
> > Some drivers (lis3lv02d) rely on the fact that the IRQ gets assigned or
> > not to trigger a different behavior (exposing /dev/freefall in this case).
> > 
> > Provide a way for others to know who set the IRQ and so they can behave
> > accordingly.
> > 
> > Signed-off-by: Benjamin Tissoires <benjamin.tissoires@xxxxxxxxxx>
> > ---
> >  drivers/i2c/i2c-core.c |  7 +++++++
> >  include/linux/i2c.h    | 11 +++++++++++
> >  2 files changed, 18 insertions(+)
> > 
> > diff --git a/drivers/i2c/i2c-core.c b/drivers/i2c/i2c-core.c
> > index cf9e396..226c75d 100644
> > --- a/drivers/i2c/i2c-core.c
> > +++ b/drivers/i2c/i2c-core.c
> > @@ -935,8 +935,12 @@ static int i2c_device_probe(struct device *dev)
> >  			irq = of_irq_get_byname(dev->of_node, "irq");
> >  			if (irq == -EINVAL || irq == -ENODATA)
> >  				irq = of_irq_get(dev->of_node, 0);
> > +			if (irq > 0)
> > +				client->irq_source = I2C_IRQ_SOURCE_OF;
> >  		} else if (ACPI_COMPANION(dev)) {
> >  			irq = acpi_dev_gpio_irq_get(ACPI_COMPANION(dev), 0);
> > +			if (irq > 0)
> > +				client->irq_source = I2C_IRQ_SOURCE_ACPI;
> >  		}
> >  		if (irq == -EPROBE_DEFER)
> >  			return irq;
> > @@ -947,6 +951,8 @@ static int i2c_device_probe(struct device *dev)
> >  		if (irq < 0) {
> >  			dev_dbg(dev, "Using Host Notify IRQ\n");
> >  			irq = i2c_smbus_host_notify_to_irq(client);
> > +			if (irq > 0)
> > +				client->irq_source = I2C_IRQ_SOURCE_HOST_NOTIFY;
> >  		}
> >  		if (irq < 0)
> >  			irq = 0;
> > @@ -1317,6 +1323,7 @@ i2c_new_device(struct i2c_adapter *adap, struct i2c_board_info const *info)
> >  	client->flags = info->flags;
> >  	client->addr = info->addr;
> >  	client->irq = info->irq;
> > +	client->irq_source = I2C_IRQ_SOURCE_PLATFORM;
> >  
> >  	strlcpy(client->name, info->type, sizeof(client->name));
> >  
> > diff --git a/include/linux/i2c.h b/include/linux/i2c.h
> > index b2109c5..7d0368d 100644
> > --- a/include/linux/i2c.h
> > +++ b/include/linux/i2c.h
> > @@ -213,6 +213,13 @@ struct i2c_driver {
> >  };
> >  #define to_i2c_driver(d) container_of(d, struct i2c_driver, driver)
> >  
> > +enum i2c_irq_source {
> > +	I2C_IRQ_SOURCE_PLATFORM,
> > +	I2C_IRQ_SOURCE_OF,
> > +	I2C_IRQ_SOURCE_ACPI,
> > +	I2C_IRQ_SOURCE_HOST_NOTIFY,
> > +};
> > +
> >  /**
> >   * struct i2c_client - represent an I2C slave device
> >   * @flags: I2C_CLIENT_TEN indicates the device uses a ten bit chip address;
> > @@ -227,6 +234,9 @@ struct i2c_driver {
> >   *	userspace_devices list
> >   * @slave_cb: Callback when I2C slave mode of an adapter is used. The adapter
> >   *	calls it to pass on slave events to the slave driver.
> > + * @irq_source: Enum which provides the source of the IRQ. Useful to know
> > + * 	if the IRQ was issued from Host Notify or if it was provided by an other
> > + * 	component.
> 
> I'd think some documentation somewhere makes sense why we need to
> distinguish this in some cases?

I'd rather drivers be oblivious of the source of interrupt. If they need
to distinguish between them that means that our IRQ abstration failed.

> 
> >   *
> >   * An i2c_client identifies a single device (i.e. chip) connected to an
> >   * i2c bus. The behaviour exposed to Linux is defined by the driver
> > @@ -245,6 +255,7 @@ struct i2c_client {
> >  #if IS_ENABLED(CONFIG_I2C_SLAVE)
> >  	i2c_slave_cb_t slave_cb;	/* callback for slave mode	*/
> >  #endif
> > +	enum i2c_irq_source irq_source;	/* which component assigned the irq */
> >  };
> >  #define to_i2c_client(d) container_of(d, struct i2c_client, dev)
> > 
> > Dmitry, Wolfram, Jean, would this be acceptable for you?
> 
> Adding something to i2c_driver is not exactly cheap, but from what I
> glimpsed from this thread, this is one of the cleanest solution to this
> problem?
> 

As Benjamin said, it is really property of device [instance], not
driver. I.e. driver could handle both wired IRQ and HostNotify-based
scheme similarly, it is device (and board) that knows how stuff is
connected.

Maybe we could do something like this (untested):