pwm: Provide pwmchip_alloc() function and a devm variant of it

This function allocates a struct pwm_chip and driver data. Compared to
the status quo the split into pwm_chip and driver data is new, otherwise
it doesn't change anything relevant (yet).

The intention is that after all drivers are switched to use this
allocation function, its possible to add a struct device to struct
pwm_chip to properly track the latter's lifetime without touching all
drivers again. Proper lifetime tracking is a necessary precondition to
introduce character device support for PWMs (that implements atomic
setting and doesn't suffer from the sysfs overhead of the /sys/class/pwm
userspace support).

The new function pwmchip_priv() (obviously?) only works for chips
allocated with pwmchip_alloc().

Link: https://lore.kernel.org/r/9577d6053a5a52536057dc8654ff567181c2da82.1707900770.git.u.kleine-koenig@pengutronix.de
Signed-off-by: Uwe Kleine-König <u.kleine-koenig@pengutronix.de>

1 files changed, 58 insertions, 0 deletions

diff --git a/drivers/pwm/core.c b/drivers/pwm/core.c
index 830a697826af..d70f793ce4b3 100644
--- a/drivers/pwm/core.c
+++ b/drivers/pwm/core.c
@@ -454,6 +454,64 @@ of_pwm_single_xlate(struct pwm_chip *chip, const struct of_phandle_args *args)
 }
 EXPORT_SYMBOL_GPL(of_pwm_single_xlate);
 
+#define PWMCHIP_ALIGN ARCH_DMA_MINALIGN
+
+static void *pwmchip_priv(struct pwm_chip *chip)
+{
+	return (void *)chip + ALIGN(sizeof(*chip), PWMCHIP_ALIGN);
+}
+
+/* This is the counterpart to pwmchip_alloc() */
+void pwmchip_put(struct pwm_chip *chip)
+{
+	kfree(chip);
+}
+EXPORT_SYMBOL_GPL(pwmchip_put);
+
+struct pwm_chip *pwmchip_alloc(struct device *parent, unsigned int npwm, size_t sizeof_priv)
+{
+	struct pwm_chip *chip;
+	size_t alloc_size;
+
+	alloc_size = size_add(ALIGN(sizeof(*chip), PWMCHIP_ALIGN), sizeof_priv);
+
+	chip = kzalloc(alloc_size, GFP_KERNEL);
+	if (!chip)
+		return ERR_PTR(-ENOMEM);
+
+	chip->dev = parent;
+	chip->npwm = npwm;
+
+	pwmchip_set_drvdata(chip, pwmchip_priv(chip));
+
+	return chip;
+}
+EXPORT_SYMBOL_GPL(pwmchip_alloc);
+
+static void devm_pwmchip_put(void *data)
+{
+	struct pwm_chip *chip = data;
+
+	pwmchip_put(chip);
+}
+
+struct pwm_chip *devm_pwmchip_alloc(struct device *parent, unsigned int npwm, size_t sizeof_priv)
+{
+	struct pwm_chip *chip;
+	int ret;
+
+	chip = pwmchip_alloc(parent, npwm, sizeof_priv);
+	if (IS_ERR(chip))
+		return chip;
+
+	ret = devm_add_action_or_reset(parent, devm_pwmchip_put, chip);
+	if (ret)
+		return ERR_PTR(ret);
+
+	return chip;
+}
+EXPORT_SYMBOL_GPL(devm_pwmchip_alloc);
+
 static void of_pwmchip_add(struct pwm_chip *chip)
 {
 	if (!pwmchip_parent(chip) || !pwmchip_parent(chip)->of_node)