On 1/25/24 6:09 AM, Uwe Kleine-König wrote:
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 devm_pwmchip_alloc().
I think this looks good. Two questions:
- Should you explicitly align the private data? Or do you believe
the default alignment (currently pointer size aligned) is adequate?
- Is there a non-devres version of the allocation function?
-Alex
Signed-off-by: Uwe Kleine-König <u.kleine-koenig@xxxxxxxxxxxxxx>
---
.../driver-api/driver-model/devres.rst | 1 +
Documentation/driver-api/pwm.rst | 10 ++++----
drivers/pwm/core.c | 25 +++++++++++++++++++
include/linux/pwm.h | 2 ++
4 files changed, 33 insertions(+), 5 deletions(-)
diff --git a/Documentation/driver-api/driver-model/devres.rst b/Documentation/driver-api/driver-model/devres.rst
index c5f99d834ec5..e4df72c408d2 100644
--- a/Documentation/driver-api/driver-model/devres.rst
+++ b/Documentation/driver-api/driver-model/devres.rst
@@ -420,6 +420,7 @@ POWER
devm_reboot_mode_unregister()
PWM
+ devm_pwmchip_alloc()
devm_pwmchip_add()
devm_pwm_get()
devm_fwnode_pwm_get()
diff --git a/Documentation/driver-api/pwm.rst b/Documentation/driver-api/pwm.rst
index 3c28ccc4b611..cee66c7f0335 100644
--- a/Documentation/driver-api/pwm.rst
+++ b/Documentation/driver-api/pwm.rst
@@ -143,11 +143,11 @@ to implement the pwm_*() functions itself. This means that it's impossible
to have multiple PWM drivers in the system. For this reason it's mandatory
for new drivers to use the generic PWM framework.
-A new PWM controller/chip can be added using pwmchip_add() and removed
-again with pwmchip_remove(). pwmchip_add() takes a filled in struct
-pwm_chip as argument which provides a description of the PWM chip, the
-number of PWM devices provided by the chip and the chip-specific
-implementation of the supported PWM operations to the framework.
+A new PWM controller/chip can be allocated using devm_pwmchip_alloc, then added
+using pwmchip_add() and removed again with pwmchip_remove(). pwmchip_add()
+takes a filled in struct pwm_chip as argument which provides a description of
+the PWM chip, the number of PWM devices provided by the chip and the
+chip-specific implementation of the supported PWM operations to the framework.
When implementing polarity support in a PWM driver, make sure to respect the
signal conventions in the PWM framework. By definition, normal polarity
diff --git a/drivers/pwm/core.c b/drivers/pwm/core.c
index 1b4c3d0caa82..b821a2b0b172 100644
--- a/drivers/pwm/core.c
+++ b/drivers/pwm/core.c
@@ -454,6 +454,31 @@ of_pwm_single_xlate(struct pwm_chip *chip, const struct of_phandle_args *args)
}
EXPORT_SYMBOL_GPL(of_pwm_single_xlate);
+static void *pwmchip_priv(struct pwm_chip *chip)
+{
+ return (void *)chip + sizeof(*chip);
+}
+
+struct pwm_chip *devm_pwmchip_alloc(struct device *parent, unsigned int npwm, size_t sizeof_priv)
+{
+ struct pwm_chip *chip;
+ size_t alloc_size;
+
+ alloc_size = size_add(sizeof(*chip), sizeof_priv);
+
+ chip = devm_kzalloc(parent, 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(devm_pwmchip_alloc);
+
static void of_pwmchip_add(struct pwm_chip *chip)
{
if (!chip->dev || !chip->dev->of_node)
diff --git a/include/linux/pwm.h b/include/linux/pwm.h
index 2c49d2fe2fe7..8bc7504aa7d4 100644
--- a/include/linux/pwm.h
+++ b/include/linux/pwm.h
@@ -403,6 +403,8 @@ static inline bool pwm_might_sleep(struct pwm_device *pwm)
int pwm_capture(struct pwm_device *pwm, struct pwm_capture *result,
unsigned long timeout);
+struct pwm_chip *devm_pwmchip_alloc(struct device *parent, unsigned int npwm, size_t sizeof_priv);
+
int __pwmchip_add(struct pwm_chip *chip, struct module *owner);
#define pwmchip_add(chip) __pwmchip_add(chip, THIS_MODULE)
void pwmchip_remove(struct pwm_chip *chip);
