On Wed, Dec 08, 2021 at 05:58:30AM PST, Jonathan Neuschäfer wrote:

Hi,

On Wed, Dec 08, 2021 at 01:24:18PM +0200, Andy Shevchenko wrote:

quoted

On Tuesday, December 7, 2021, Jonathan Neuschäfer [off-list ref]

<snip>

quoted

quoted

+static void wpcm450_gpio_irqhandler(struct irq_desc *desc)
+{
+       struct wpcm450_gpio *gpio = gpiochip_get_data(irq_desc_
get_handler_data(desc));
+       struct wpcm450_pinctrl *pctrl = gpio->pctrl;
+       struct irq_chip *chip = irq_desc_get_chip(desc);
+       unsigned long pending;
+       unsigned long flags;
+       unsigned long ours;
+       unsigned int bit;
+
+       ours = ((1UL << gpio->num_irqs) - 1) << gpio->first_irq_bit;

BIT()

I'll use it, but in this case, I think it doesn't simplify much the
whole expression all that much. Is there perhaps a macro that
constructs a continuous bitmask of N bits, perhaps additionally
left-shifted by M bits?

Maybe somewhere in the bitmap_* API...

There's GENMASK(), though it takes a high bit and low bit rather than a
bit position and count, so it'd require a small bit of arithmetic, e.g.

  lastbit = gpio->first_irq_bit + gpio->num_irqs - 1;
  ours = GENMASK(lastbit, gpio->first_irq_bit);

or a manual shift:

  ours = GENMASK(gpio->num_irqs - 1, 0) << gpio->first_irq_bit;

(I don't have any terribly strong opinions on which of these is best,
personally.)



Zev