linux-kernel - Re: [PATCH v5 2/3] gpio: ch341: add GPIO MFD cell driver for the CH341

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Date:   Wed, 15 Jun 2022 20:29:31 -0500
From:   Frank Zago <frank@...o.net>
To:     Johan Hovold <johan@...nel.org>
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        linux-kernel@...r.kernel.org,
        Bartosz Golaszewski <bgolaszewski@...libre.com>,
        Wolfram Sang <wsa@...nel.org>, linux-usb@...r.kernel.org,
        Lee Jones <lee.jones@...aro.org>,
        Linus Walleij <linus.walleij@...aro.org>,
        linux-gpio@...r.kernel.org, linux-i2c@...r.kernel.org
Subject: Re: [PATCH v5 2/3] gpio: ch341: add GPIO MFD cell driver for the
 CH341

On 5/23/22 11:16, Johan Hovold wrote:

>> +static void ch341_complete_intr_urb(struct urb *urb)
>> +{
>> +	struct ch341_gpio *dev = urb->context;
>> +	int rc;
>> +
>> +	if (urb->status) {
>> +		usb_unanchor_urb(dev->irq_urb);
> 
> URBs are unanchored by USB core on completion.

Fixed.

> 
>> +static void ch341_gpio_irq_enable(struct irq_data *data)
>> +{
>> +	struct ch341_gpio *dev = irq_data_get_irq_chip_data(data);
>> +	int rc;
>> +
>> +	/*
>> +	 * The URB might have just been unlinked in
>> +	 * ch341_gpio_irq_disable, but the completion handler hasn't
>> +	 * been called yet.
>> +	 */
>> +	if (!usb_wait_anchor_empty_timeout(&dev->irq_urb_out, 5000))
>> +		usb_kill_anchored_urbs(&dev->irq_urb_out);
>> +
>> +	usb_anchor_urb(dev->irq_urb, &dev->irq_urb_out);
>> +	rc = usb_submit_urb(dev->irq_urb, GFP_ATOMIC);
>> +	if (rc)
>> +		usb_unanchor_urb(dev->irq_urb);
> 
> This looks confused and broken.
> 
> usb_kill_anchored_urbs() can sleep so either calling it is broken or
> using GFP_ATOMIC is unnecessary.

Right, that function can sleep. I changed GFP_ATOMIC to GFP_KERNEL.

> 
> And isn't this function called multiple times when enabling more than
> one irq?!

There's only one IRQ, so only one URB will be posted at a time. It
is reposted as soon as it comes back unless the IRQ is disabled or
the device stops.


> 
>> +}
>> +
>> +static void ch341_gpio_irq_disable(struct irq_data *data)
>> +{
>> +	struct ch341_gpio *dev = irq_data_get_irq_chip_data(data);
>> +
>> +	usb_unlink_urb(dev->irq_urb);
> 
> Same here...
> 
>> +}
>> +
>> +static int ch341_gpio_remove(struct platform_device *pdev)
>> +{
>> +	struct ch341_gpio *dev = platform_get_drvdata(pdev);
>> +
>> +	usb_kill_anchored_urbs(&dev->irq_urb_out);
> 
> You only have one URB...
> 
> And what prevents it from being resubmitted here?

I don't see what would resubmit it here. The gpio is being released.

Frank.