linux-kernel - Resend Re: [PATCH v6] usb:serial:pl2303: add GPIOs interface on PL2303

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Date:	Tue, 5 Aug 2014 01:15:36 +0800
From:	Wang YanQing <udknight@...il.com>
To:	Johan Hovold <johan@...nel.org>
Cc:	gregkh@...uxfoundation.org, linus.walleij@...aro.org,
	jhovold@...il.com, andi@...as.de, dforsi@...il.com,
	gnomes@...rguk.ukuu.org.uk, linux-usb@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: Resend Re: [PATCH v6] usb:serial:pl2303: add GPIOs interface on
 PL2303

I change my system recently, and sendmail has trouble
to send mails to kernel mail list, so I resend it 
with my old system.

Ok, before I send out next version, I still has some
vague places, see below:
	
On Mon, Aug 04, 2014 at 04:00:32PM +0200, Johan Hovold wrote:
> > +config USB_SERIAL_PL2303_GPIO
> > +	bool "USB Prolific 2303 Single Port GPIOs support"
> > +	depends on USB_SERIAL_PL2303 && GPIOLIB
> > +	---help---
> > +	  Say Y here if you want to use the GPIOs on PL2303 USB Serial single port
> > +	  adapter from Prolific.
> > +
> > +	  It supports 2 GPIOs on PL2303HX currently,
> > +	  if unsure, say N.
> 
> You can drop the "unsure" bit (or at least split it into two sentences).

I don't understand here, what is your meaning?
I add "if unsure, say N" to make checkpatch.pl happy,
it seems like checkpatch.pl want at least two lines here.

> I noticed that setting direction to output and setting the gpio high has
> no effect on the read-back value (i.e. I still read back 0) for my
> pl2303hx (note that my device has no easily accessible gpios so I
> haven't verified the actual state of the output pin).
> 
> What happens on your system? Is the read-back value still 0, even when
> the GPIO output is actually high? Should we return the cached value in
> this case?

If i set direction to output, then I could control gpio high and low
by set 1 or 0, and the read-back value is 1 or 0 according to high and
low(I test high and low by oscillscope)

I test it with my pl2303hx with only two gpios.

Could you use usbmon to see whether the traffic is right according
to comment in struct pl2303_gpio?

> > +	spriv->gpio->index = 0x00;
> > +	spriv->gpio->serial = serial;
> > +
> > +	mutex_lock(&gpiochip_lock);
> > +	minor = idr_alloc(&gpiochip_minor, serial, 0, 0, GFP_KERNEL);
> > +	if (minor < 0) {
> > +		mutex_unlock(&gpiochip_lock);
> > +		ret = minor;
> > +		goto ERROR1;
> > +	}
> > +	spriv->gpio->minor = minor;
> > +	mutex_unlock(&gpiochip_lock);
> > +
> > +	label = kasprintf(GFP_KERNEL, "pl2303-gpio%d",
> > +			  spriv->gpio->minor);
> > +	if (label == NULL) {
> > +		ret = -ENOMEM;
> > +		goto ERROR2;
> > +	}
> 
> The id allocation and label generation is just overkill (if anything,
> you'd want the generated name to include the interface name rather
> than some new random number).
> 
> But as we can always find the parent device via sysfs, simply set the
> label to "pl2303".
I don't understand here, I want to fix we can't distinguish
multi pl2303 gpios in kernel space, not userspace by different
label name when there are more than one pl2303.

I find usb-serial use idr_alloc to manage minor, so I use it,
I hope the label's name looks like below:
pl2303-gpio0, pl2303-gpio1.

Because gpiolib could use label to find out specified gpio chio,
then we could distinguish them by standard gpio interface, after
acquire pl2303 gpio by different label name, we could test their
parent device to make sure whether right one or not, and release
it when not.

With different label names, we could predict their name depend on
fix usb bus scanning order in a fix hardare environment, then we could
acquire "right" pl2303 gpio chip by pl2303-gpio0, pl2303-gpio1.

Thanks.
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