linux-kernel - Re: [PATCH v4 2/3] i2c: add support for Cypress CYUSBS234 USB-I2C adapter

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Date:	Sat, 13 Dec 2014 13:14:26 +0100
From:	Wolfram Sang <wsa@...-dreams.de>
To:	Muthu Mani <muth@...ress.com>
Cc:	Samuel Ortiz <sameo@...ux.intel.com>,
	Lee Jones <lee.jones@...aro.org>,
	Linus Walleij <linus.walleij@...aro.org>,
	Alexandre Courbot <gnurou@...il.com>,
	"gregkh@...uxfoundation.org" <gregkh@...uxfoundation.org>,
	Johan Hovold <johan@...nel.org>,
	"linux-usb@...r.kernel.org" <linux-usb@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"linux-i2c@...r.kernel.org" <linux-i2c@...r.kernel.org>,
	"linux-gpio@...r.kernel.org" <linux-gpio@...r.kernel.org>,
	Rajaram Regupathy <rera@...ress.com>
Subject: Re: [PATCH v4 2/3] i2c: add support for Cypress CYUSBS234 USB-I2C
 adapter


> For repeated start (Sr) scenario, the STOP bit will not be set. For
> dummy write scenario (writing EEPROM address from I2C EEPROM slave),
> the STOP bit should not be set. But, for normal I2C write, the STOP
> bit should be set. We provide control to user to control when to
> STOP/NAK to handle different scenarios.

No, your driver needs to do all of that.

> The reset is an additional provision given to user to reset the I2C
> read or write engines. It does not require unloading I2C kernel
> module. The status indicates the information about the last i2c
> read/write operation.

I don't see the need for the user to do this. Better skip it,
there should be a real need for userspace API.

> In this version of the driver, we handle only single i2c message. In
> future iterations, we will add support for multiple i2c messages.

Then please resubmit when all this is done. It is OK to add features
incrementally, but hey, the essential things should be there right from
the beginning. Also, it would be nice if you told me your plans about
incrementally working on it right from the beginning. That would have
saved me a bit of reviewing time, a resource which is too scarce
already.


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