linux-kernel - Re: [PATCH v8 2/4] i2c-smbus: add SMBus Host Notify support

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Date:	Mon, 18 Jul 2016 11:37:21 +0200
From:	Jean Delvare <jdelvare@...e.de>
To:	Benjamin Tissoires <benjamin.tissoires@...hat.com>
Cc:	Wolfram Sang <wsa@...-dreams.de>, Jonathan Corbet <corbet@....net>,
	Corey Minyard <minyard@....org>,
	Guenter Roeck <linux@...ck-us.net>,
	Dmitry Torokhov <dmitry.torokhov@...il.com>,
	Andrew Duggan <aduggan@...aptics.com>,
	Christopher Heiny <cheiny@...aptics.com>,
	linux-i2c@...r.kernel.org, linux-doc@...r.kernel.org,
	linux-kernel@...r.kernel.org, linux-input@...r.kernel.org
Subject: Re: [PATCH v8 2/4] i2c-smbus: add SMBus Host Notify support

[As it doesn't look like this message was delivered, I am sending it
again. I apologize if this is a duplicate for some of you.]

Hi Benjamin, Wolfram,

Sorry for being late to the party. I finally found some time to look at
the patches. Looks good overall, with just two minor comments:

On jeu., 2016-06-09 at 16:53 +0200, Benjamin Tissoires wrote:
> SMBus Host Notify allows a slave device to act as a master on a bus to
> notify the host of an interrupt. On Intel chipsets, the functionality
> is directly implemented in the firmware. We just need to export a
> function to call .alert() on the proper device driver.
> 
> i2c_handle_smbus_host_notify() behaves like i2c_handle_smbus_alert().
> When called, it schedules a task that will be able to sleep to go through
> the list of devices attached to the adapter.
> 
> The current implementation allows one Host Notification to be scheduled
> while an other is running.
> 
> Tested-by: Andrew Duggan <aduggan@...aptics.com>
> Signed-off-by: Benjamin Tissoires <benjamin.tissoires@...hat.com>
> ---
> (...)
> diff --git a/drivers/i2c/i2c-smbus.c b/drivers/i2c/i2c-smbus.c
> index 3b6765a..f574995 100644
> --- a/drivers/i2c/i2c-smbus.c
> +++ b/drivers/i2c/i2c-smbus.c
> (...)
> +/**
> + * i2c_handle_smbus_host_notify - Forward a Host Notify event to the correct
> + * I2C client.
> + * @host_notify: the struct host_notify attached to the relevant adapter
> + * @data: the Host Notify data which contains the payload and address of the
> + * client

Doesn't look correct. The data parameter doesn't contain the address,
that would be in the (undocumented) address parameter. I'll send a
patch.

> diff --git a/include/linux/i2c-smbus.h b/include/linux/i2c-smbus.h
> index 8f1b086..4ac95bb 100644
> --- a/include/linux/i2c-smbus.h
> +++ b/include/linux/i2c-smbus.h
> (...)
> +#if IS_ENABLED(CONFIG_I2C_SMBUS)
> +struct smbus_host_notify *i2c_setup_smbus_host_notify(struct i2c_adapter *adap);
> +int i2c_handle_smbus_host_notify(struct smbus_host_notify *host_notify,
> +				 unsigned short addr, unsigned int data);
> +#else
> +static inline struct smbus_host_notify *
> +i2c_setup_smbus_host_notify(struct i2c_adapter *adap)
> +{
> +	return NULL;
> +}
> +
> +static inline int
> +i2c_handle_smbus_host_notify(struct smbus_host_notify *host_notify,
> +			     unsigned short addr, unsigned int data)
> +{
> +	return 0;
> +}
> +#endif /* I2C_SMBUS */

You provide stubs for SMBus Host Notify support if CONFIG_I2C_SMBUS is
not selected. There are no such stubs for SMBus Alert support, for which
I assumed drivers would select I2C_SMBUS if they have support. Which is
what you are actually doing for i2c-i801 in a latter patch.

Is there any reason for this difference? For consistency I'd rather
provide stubs for all or none. My preference being for none, unless you
have a use case which requires them.

-- 
Jean Delvare
SUSE L3 Support