gpio: bcm-kona: reduce the number of memory allocations

Simplify allocation by using a flexible array member.

Use __counted_by for extra runtime analysis.

Shuffle some code as __counted_by requires the counting variable to be
set right after allocation.

Signed-off-by: Rosen Penev <[e-mail]>
Link: https://patch.msgid.link/[e-mail]
Signed-off-by: Bartosz Golaszewski <[e-mail]>

drivers/gpio/gpio-bcm-kona.c

···
 #define LOCK_CODE				0xffffffff
 #define UNLOCK_CODE				0x00000000
 
-struct bcm_kona_gpio {
-	void __iomem *reg_base;
-	int num_bank;
-	raw_spinlock_t lock;
-	struct gpio_chip gpio_chip;
-	struct irq_domain *irq_domain;
-	struct bcm_kona_gpio_bank *banks;
-};
-
 struct bcm_kona_gpio_bank {
 	int id;
 	int irq;
···
 	u8 gpio_unlock_count[GPIO_PER_BANK];
 	/* Used in the interrupt handler */
 	struct bcm_kona_gpio *kona_gpio;
+};
+
+struct bcm_kona_gpio {
+	void __iomem *reg_base;
+	int num_bank;
+	raw_spinlock_t lock;
+	struct gpio_chip gpio_chip;
+	struct irq_domain *irq_domain;
+	struct bcm_kona_gpio_bank banks[] __counted_by(num_bank);
 };
 
 static inline void bcm_kona_gpio_write_lock_regs(void __iomem *reg_base,
···
 	int ret;
 	int i;
 
-	kona_gpio = devm_kzalloc(dev, sizeof(*kona_gpio), GFP_KERNEL);
-	if (!kona_gpio)
-		return -ENOMEM;
-
-	kona_gpio->gpio_chip = template_chip;
-	chip = &kona_gpio->gpio_chip;
 	ret = platform_irq_count(pdev);
 	if (!ret) {
 		dev_err(dev, "Couldn't determine # GPIO banks\n");
···
 	} else if (ret < 0) {
 		return dev_err_probe(dev, ret, "Couldn't determine GPIO banks\n");
 	}
+
+	kona_gpio = devm_kzalloc(dev, struct_size(kona_gpio, banks, ret), GFP_KERNEL);
+	if (!kona_gpio)
+		return -ENOMEM;
+
 	kona_gpio->num_bank = ret;
 
 	if (kona_gpio->num_bank > GPIO_MAX_BANK_NUM) {
···
 			GPIO_MAX_BANK_NUM);
 		return -ENXIO;
 	}
-	kona_gpio->banks = devm_kcalloc(dev,
-					kona_gpio->num_bank,
-					sizeof(*kona_gpio->banks),
-					GFP_KERNEL);
-	if (!kona_gpio->banks)
-		return -ENOMEM;
 
+	kona_gpio->gpio_chip = template_chip;
+	chip = &kona_gpio->gpio_chip;
 	chip->parent = dev;
 	chip->ngpio = kona_gpio->num_bank * GPIO_PER_BANK;