linux-kernel - Re: [PATCH v5 6/6] i2c: use an IRQ to report Host Notify events, not alert

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Date:   Mon, 7 Nov 2016 01:20:35 +0100
From:   Wolfram Sang <wsa@...-dreams.de>
To:     Benjamin Tissoires <benjamin.tissoires@...hat.com>
Cc:     Dmitry Torokhov <dmitry.torokhov@...il.com>,
        linux-i2c@...r.kernel.org, linux-kernel@...r.kernel.org,
        Jean Delvare <jdelvare@...e.com>
Subject: Re: [PATCH v5 6/6] i2c: use an IRQ to report Host Notify events, not
 alert

On Thu, Oct 13, 2016 at 02:10:40PM +0200, Benjamin Tissoires wrote:
> The current SMBus Host Notify implementation relies on .alert() to
> relay its notifications. However, the use cases where SMBus Host
> Notify is needed currently is to signal data ready on touchpads.
> 
> This is closer to an IRQ than a custom API through .alert().
> Given that the 2 touchpad manufacturers (Synaptics and Elan) that
> use SMBus Host Notify don't put any data in the SMBus payload, the
> concept actually matches one to one.

I see the advantages. The only question I have: What if we encounter
devices in the future which do put data in the payload? Can this
mechanism be extended to handle that?

> 
> Benefits are multiple:
> - simpler code and API: the client will just have an IRQ, and
>   nothing needs to be added in the adapter beside internally
>   enabling it.
> - no more specific workqueue, the threading is handled by IRQ core
>   directly (when required)
> - no more races when removing the device (the drivers are already
>   required to disable irq on remove)
> - simpler handling for drivers: use plain regular IRQs
> - no more dependency on i2c-smbus for i2c-i801 (and any other adapter)
> - the IRQ domain is created automatically when the adapter exports
>   the Host Notify capability
> - the IRQ are assign only if ACPI, OF and the caller did not assign
>   one already
> - the domain is automatically destroyed on remove
> - fewer lines of code (minus 20, yeah!)
> 
> Signed-off-by: Benjamin Tissoires <benjamin.tissoires@...hat.com>

Thanks for keeping at it!


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