linux-kernel - Re: Microchip USB Hub Driver Harmonization

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Date:   Wed, 17 May 2017 18:01:52 +0200
From:   Krzysztof Kozlowski <krzk@...nel.org>
To:     Richard Leitner <richard.leitner@...data.com>
Cc:     Linux USB List <linux-usb@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Javier Martinez Canillas <javier@....samsung.com>,
        Richard Leitner <dev@...l1n.net>,
        Stephen Boyd <stephen.boyd@...aro.org>
Subject: Re: Microchip USB Hub Driver Harmonization

On Wed, May 17, 2017 at 12:58:38PM +0200, Richard Leitner wrote:
> Hello,
> due to the fact (all?) the Microchip (former SMSC) USB hubs share the
> same I2C configuration interface, I'm currently working on harmonizing
> those USB Hub drivers. Currently this affects the usb251xb, usb3503 and
> usb4604 drivers. To avoid preventable efforts (and patch versions) I
> have some question on the preferred implementation:
> 
> 1. Currently usb251xb uses i2c_smbus_*, usb3503 uses regmap_* and
> usb4604 uses i2c_master_* functions for the hub configuration. What
> would be the preferred solution?

regmap? It is already widely used for I2C drivers. I think most (or even
all?) new I2C drivers use regmap. It hides the real bus between common
regmap API.

> 2. What would be a good prefix for common headers/functions/macros/etc.?
> I thought of "mcusbhub"... Would that be OK? Or are there any
> conventions/better proposals on that?

If you are going to develop one driver for entire family, then you could
even choose just one name. Let's say the most generic.

I don't quite understand the meaning behind "harmonizing drivers".

> 3. Currently only usb3503 supports "platform data". Is this still needed
> or may it be removed?

I think it is still used, e.g. by:
arch/arm/boot/dts/exynos5250-spring.dts

Best regards,
Krzysztof