linux-kernel - Re: [PATCHv5 2/4] usb: gadget: replace "is_dualspeed" with "max

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Date:	Fri, 09 Sep 2011 16:14:21 +0200
From:	"Michal Nazarewicz" <mnazarewicz@...gle.com>
To:	"Alan Stern" <stern@...land.harvard.edu>,
	"Felipe Balbi" <balbi@...com>,
	"Michal Nazarewicz" <mnazarewicz@...gle.com>
Cc:	"Sebastian Andrzej Siewior" <bigeasy@...utronix.de>,
	"Yang Rui Rui" <ruirui.r.yang@...to.com>,
	"Dave Young" <hidave.darkstar@...il.com>,
	linux-usb@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCHv5 2/4] usb: gadget: replace "is_dualspeed" with
 "max_speed"

On Fri, 26 Aug 2011 15:18:35 +0200, Michal Nazarewicz  
<mnazarewicz@...gle.com> wrote:
> This commit replaces usb_gadget's is_dualspeed field with
> a max_speed field.
> ---
>
> I was unable to figure out how to create a symlink in
> non-race-condition way so for now I've created both speed and
> current_speed attributes.  This needs to get fixed before getting
> merged.
>
> I would even consider just removing speed since udc-core got merged
> only in 3.1, so maybe it won't be such a big issue?

I've dug a bit deeper and could not find *any* way of creating the
speed -> current_speed symlink.  sysfs_create_link() requires target
to be an kobject and as far as I can see attributes don't have one.

So I see the following possibilities:

1. Leave speed only (as Felipe noticed, this may be confusing for
    users since there will be "speed" and "maximum_speed").
2. Rename it to current_speed without transition period (udc-core is
    young so maybe no one will notice, but that won't be very nice).
3. Add current_speed and mark speed deprecated (this may be confusing
    because there will be two attributes with the same value).

>  static DEVICE_ATTR(soft_connect, S_IWUSR, NULL, usb_udc_softconn_store);
> -static ssize_t usb_udc_speed_show(struct device *dev,
> +#define USB_UDC_SPEED_ATTR(name, param)					\
> +ssize_t usb_udc_##param##_show(struct device *dev,			\
> +		struct device_attribute *attr, char *buf)		\
> +{									\
> +	struct usb_udc *udc = container_of(dev, struct usb_udc, dev);	\
> +	return snprintf(buf, PAGE_SIZE, "%s\n",				\
> +			usb_speed_string(udc->gadget->param));		\
> +}									\
> +static DEVICE_ATTR(name, S_IRUSR, usb_udc_##param##_show, NULL)
> +
> +static USB_UDC_SPEED_ATTR(current_speed, speed);
> +static USB_UDC_SPEED_ATTR(maximum_speed, max_speed);
> +/* XXX Change to symlink? */
> +/* TODO: Scheduled for removal in 3.8. */
> +static DEVICE_ATTR(speed, S_IRUSR, usb_udc_speed_show, NULL);

-- 
Best regards,                                         _     _
.o. | Liege of Serenely Enlightened Majesty of      o' \,=./ `o
..o | Computer Science,  Michal "mina86" Nazarewicz    (o o)
ooo +-----<email/xmpp: mnazarewicz@...gle.com>-----ooO--(_)--Ooo--
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