linux-kernel - Re: [PATCH v3 1/3] mfd: add support for Cypress CYUSBS234 USB Serial Bridge controller

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Message-ID: <20141009105950.GP20647@lee--X1>
Date:	Thu, 9 Oct 2014 11:59:50 +0100
From:	Lee Jones <lee.jones@...aro.org>
To:	Johan Hovold <johan@...nel.org>
Cc:	Muthu Mani <muth@...ress.com>,
	Samuel Ortiz <sameo@...ux.intel.com>,
	Wolfram Sang <wsa@...-dreams.de>,
	Linus Walleij <linus.walleij@...aro.org>,
	Alexandre Courbot <gnurou@...il.com>,
	gregkh@...uxfoundation.org, linux-i2c@...r.kernel.org,
	linux-gpio@...r.kernel.org, linux-usb@...r.kernel.org,
	linux-kernel@...r.kernel.org, Rajaram Regupathy <rera@...ress.com>
Subject: Re: [PATCH v3 1/3] mfd: add support for Cypress CYUSBS234 USB Serial
 Bridge controller

On Thu, 09 Oct 2014, Johan Hovold wrote:

> On Thu, Oct 09, 2014 at 08:40:29AM +0100, Lee Jones wrote:
> > On Mon, 06 Oct 2014, Muthu Mani wrote:
> 
> > > +static int update_ep_details(struct usb_interface *interface,
> > > +				struct cyusbs23x *cyusbs)
> > > +{
> > > +	struct usb_host_interface *iface_desc;
> > > +	struct usb_endpoint_descriptor *ep;
> > > +	int i;
> > > +
> > > +	iface_desc = interface->cur_altsetting;
> > > +
> > > +	for (i = 0; i < iface_desc->desc.bNumEndpoints; ++i) {
> > > +
> > > +		ep = &iface_desc->endpoint[i].desc;
> > > +
> > > +		if (!cyusbs->bulk_in_ep_num && usb_endpoint_is_bulk_in(ep))
> > > +			cyusbs->bulk_in_ep_num = ep->bEndpointAddress;
> > > +		if (!cyusbs->bulk_out_ep_num && usb_endpoint_is_bulk_out(ep))
> > > +			cyusbs->bulk_out_ep_num = ep->bEndpointAddress;
> > > +		if (!cyusbs->intr_in_ep_num && usb_endpoint_is_int_in(ep))
> > > +			cyusbs->intr_in_ep_num = ep->bEndpointAddress;
> > > +	}
> > 
> > All of the USB specific code in this driver will require a USB Ack.
> 
> I'll review it once the incomplete gpio-driver issue has been resolved.

Okay, great.

> > > +	dev_dbg(&interface->dev, "%s intr_in=%d, bulk_in=%d, bulk_out=%d\n",
> > > +		__func__, cyusbs->intr_in_ep_num ,
> > > +		cyusbs->bulk_in_ep_num, cyusbs->bulk_out_ep_num);
> > > +
> > > +	if (!cyusbs->bulk_in_ep_num || !cyusbs->bulk_out_ep_num ||
> > > +		!cyusbs->intr_in_ep_num)
> > > +		return -ENODEV;
> > > +
> > > +	return 0;
> > > +}
> 
> [...]
> 
> > > diff --git a/include/linux/mfd/cyusbs23x.h b/include/linux/mfd/cyusbs23x.h
> 
> > > +/* Serial interfaces (I2C, SPI, UART) differ in interface subclass */
> > > +enum cy_scb_modes {
> > > +	CY_USBS_SCB_DISABLED = 0,
> > > +	CY_USBS_SCB_UART = 1,
> > > +	CY_USBS_SCB_SPI = 2,
> > > +	CY_USBS_SCB_I2C = 3
> > 
> > No need to number these.
> 
> As it's not an arbitrary enumeration, I think they should be initialised
> explicitly.

No need.  You are protected by the C Standard:

6.7.2.2 Enumeration specifiers

"If the first enumerator has no =, the value of its enumeration
constant is 0. Each subsequent enumerator with no = defines its
enumeration constant as the value of the constant expression obtained
by adding 1 to the value of the previous enumeration constant."

There's nothing arbitrary about that.

> They could be defined in the mfd driver though, as they only
> appear to be needed during probe.


-- 
Lee Jones
Linaro STMicroelectronics Landing Team Lead
Linaro.org │ Open source software for ARM SoCs
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