linux-kernel - Re: [PATCH v12 1/7] mfd: Add core driver for Nuvoton NCT6694

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Message-ID: <CAOoeyxU1-HWSfNGLrXQCgaE8gC=3Q=yF7=S_N=J=q_26Kmh5PQ@mail.gmail.com>
Date: Thu, 5 Jun 2025 15:48:38 +0800
From: Ming Yu <a0282524688@...il.com>
To: Oliver Neukum <oneukum@...e.com>
Cc: lee@...nel.org, linus.walleij@...aro.org, brgl@...ev.pl, 
	andi.shyti@...nel.org, mkl@...gutronix.de, mailhol.vincent@...adoo.fr, 
	andrew+netdev@...n.ch, davem@...emloft.net, edumazet@...gle.com, 
	kuba@...nel.org, pabeni@...hat.com, wim@...ux-watchdog.org, 
	linux@...ck-us.net, jdelvare@...e.com, alexandre.belloni@...tlin.com, 
	linux-kernel@...r.kernel.org, linux-gpio@...r.kernel.org, 
	linux-i2c@...r.kernel.org, linux-can@...r.kernel.org, netdev@...r.kernel.org, 
	linux-watchdog@...r.kernel.org, linux-hwmon@...r.kernel.org, 
	linux-rtc@...r.kernel.org, linux-usb@...r.kernel.org, 
	Ming Yu <tmyu0@...oton.com>
Subject: Re: [PATCH v12 1/7] mfd: Add core driver for Nuvoton NCT6694

Dear Oliver,

Thank you for reviewing,

Oliver Neukum <oneukum@...e.com> 於 2025年6月4日 週三 下午6:11寫道：
>
> > +static void usb_int_callback(struct urb *urb)
> > +{
> > +     struct nct6694 *nct6694 = urb->context;
> > +     unsigned int *int_status = urb->transfer_buffer;
> > +     int ret;
> > +
> > +     switch (urb->status) {
> > +     case 0:
> > +             break;
> > +     case -ECONNRESET:
> > +     case -ENOENT:
> > +     case -ESHUTDOWN:
> > +             return;
> > +     default:
> > +             goto resubmit;
> > +     }
> > +
> > +     while (*int_status) {
> > +             int irq = __ffs(*int_status);
> > +
> > +             generic_handle_irq_safe(irq_find_mapping(nct6694->domain, irq));
> > +             *int_status &= ~BIT(irq);
> > +     }
>
> Does modifying the byte have any benefit?
>

I will update the code in the next patch to use __le32 for the
variable to ensure proper endianness handling across architectures.

> > +resubmit:
> > +     ret = usb_submit_urb(urb, GFP_ATOMIC);
> > +     if (ret)
> > +             dev_warn(nct6694->dev, "Failed to resubmit urb, status %pe",  ERR_PTR(ret));
> > +}
> > +
> > +static void nct6694_irq_lock(struct irq_data *data)
> > +{
> > +     struct nct6694 *nct6694 = irq_data_get_irq_chip_data(data);
> > +
> > +     mutex_lock(&nct6694->irq_lock);
> > +}
>
> Why? Does this do anything but make it _harder_ to tell that you
> cannot take the lock in interrupt?
>

I plan to remove nct6694_irq_lock() and nct6694_bus_sync_unlock(), and
instead add the spinlock directly inside the function like this:
static void nct6694_irq_enable(struct irq_data *data)
{
    ...
    spin_lock(&nct6694->irq_lock);
    nct6694->irq_enable |= BIT(hwirq);
    spin_unlock(&nct6694->irq_lock);
}

Do you think this approach is better?


Best regards,
Ming