kernel/linux.git/drivers/pwm/core.c, branch v6.19.11

pwm: Ensure ioctl() returns a negative errno on error

2026-01-19T16:46:51+00:00

copy_to_user() returns the number of bytes not copied, thus if there is a problem a positive number. However the ioctl callback is supposed to return a negative error code on error. This error is a unfortunate as strictly speaking it became ABI with the introduction of pwm character devices. However I never saw the issue in real life -- I found this by code inspection -- and it only affects an error case where readonly memory is passed to the ioctls or the address mapping changes while the ioctl is active. Also there are already error cases returning negative values, so the calling code must be prepared to see such values already. Fixes: 9c06f26ba5f5 ("pwm: Add support for pwmchip devices for faster and easier userspace access") Signed-off-by: Uwe Kleine-König Link: https://patch.msgid.link/20260119151325.571857-2-u.kleine-koenig@baylibre.com Signed-off-by: Uwe Kleine-König

Merge branch 'pwm/th1520' into pwm/for-next

2025-11-14T10:56:14+00:00

pwm: Use %u to printf unsigned int pwm_chip::npwm and pwm_chip::id

2025-11-14T10:56:14+00:00

%u is the right conversion specifier to emit an unsigned int value. Fixes: 62099abf67a2 ("pwm: Add debugfs interface") Fixes: 0360a4873372 ("pwm: Mention PWM chip ID in /sys/kernel/debug/pwm") Signed-off-by: Uwe Kleine-König Link: https://patch.msgid.link/20251006133525.2457171-2-u.kleine-koenig@baylibre.com Signed-off-by: Uwe Kleine-König

pwm: Simplify printf to emit chip->npwm in $debugfs/pwm

2025-11-14T10:56:13+00:00

Instead of caring to correctly pluralize "PWM device(s)" using (chip->npwm != 1) ? "s" : "" or str_plural(chip->npwm) just simplify the format to not need a plural-s. Signed-off-by: Uwe Kleine-König Link: https://patch.msgid.link/20250926165702.321514-2-u.kleine-koenig@baylibre.com Signed-off-by: Uwe Kleine-König

pwm: Export `pwmchip_release` for external use

2025-11-07T09:03:53+00:00

The upcoming Rust abstraction layer for the PWM subsystem uses a custom `dev->release` handler to safely manage the lifetime of its driver data. To prevent leaking the memory of the `struct pwm_chip` (allocated by `pwmchip_alloc`), this custom handler must also call the original `pwmchip_release` function to complete the cleanup. Make `pwmchip_release` a global, exported function so that it can be called from the Rust FFI bridge. This involves removing the `static` keyword, adding a prototype to the public header, and exporting the symbol. Reviewed-by: Elle Rhumsaa Signed-off-by: Michal Wilczynski Link: https://patch.msgid.link/20251016-rust-next-pwm-working-fan-for-sending-v16-1-a5df2405d2bd@samsung.com Signed-off-by: Uwe Kleine-König

pwm: Provide a gpio device for waveform drivers

2025-09-15T09:39:44+00:00

A PWM is a more general concept than an output-only GPIO. When using duty_length = period_length the PWM looks like an active GPIO, with duty_length = 0 like an inactive GPIO. With the waveform abstraction there is enough control over the configuration to ensure that PWMs that cannot generate a constant signal at both levels error out. The pwm-pca9685 driver already provides a gpio chip. When this driver is converted to the waveform callbacks, the gpio part can just be dropped. Signed-off-by: Uwe Kleine-König Reviewed-by: Bartosz Golaszewski Link: https://lore.kernel.org/r/20250717151117.1828585-2-u.kleine-koenig@baylibre.com Signed-off-by: Uwe Kleine-König

pwm: Check actual period and duty_cycle for ignored polarity test

2025-09-15T09:39:44+00:00

When a lowlevel driver configures the wrong period that might (historically) be ok if the emitted signal has a 100% relative duty_cycle as that just corresponds to rounding down the duty_cycle to 0 which is an allowed thing to do for a lowlevel driver. Signed-off-by: Uwe Kleine-König Link: https://lore.kernel.org/r/bc511c0250ea2f6390e4209ab1ea9c08a3c18612.1751994988.git.u.kleine-koenig@baylibre.com Signed-off-by: Uwe Kleine-König

pwm: Disable PWM_DEBUG check for disabled states

2025-09-15T09:39:44+00:00

When a PWM is requested to be disabled, the result is unspecified, the only intention is to save some power. So skip all checks in this case. All but two checks already only triggered for states with .enabled = true. The first resulted in some false positive diagnostics, the other checked for a condition that depending on hardware might not be implementable. Similar if the lowlevel driver disabled the hardware this might be a valid reaction and with .enabled = false all other state parameters are unreliable, so skip further tests in this case, too. All later usages of .enabled can be assumed to yield true, and so several if conditions can be simplified. Signed-off-by: Uwe Kleine-König Link: https://lore.kernel.org/r/16d29212b09b66c286c1232b1ab0ec0f8d510aae.1751994988.git.u.kleine-koenig@baylibre.com Signed-off-by: Uwe Kleine-König

pwm: Fix incorrect variable used in error message

2025-09-15T09:39:43+00:00

The dev_err message is reporting the incorrect return value ret_tohw, it should be reporting the value in ret_fromhw. Fix this by using ret_fromhw instead of ret_tohw. Fixes: 6c5126c6406d ("pwm: Provide new consumer API functions for waveforms") Signed-off-by: Colin Ian King Link: https://lore.kernel.org/r/20250902130348.2630053-1-colin.i.king@gmail.com Cc: stable@vger.kernel.org Signed-off-by: Uwe Kleine-König

pwm: Expose PWM_WFHWSIZE in public header

2025-07-07T06:39:36+00:00

The WFHWSIZE constant defines the maximum size for the hardware-specific waveform representation buffer. It is currently local to drivers/pwm/core.c, which makes it inaccessible to external tools like bindgen. Move the constant to include/linux/pwm.h to make it part of the public API. As part of this change, rename it to PWM_WFHWSIZE to follow standard kernel conventions for namespacing macros in public headers. This allows bindgen to automatically generate a corresponding constant for the Rust PWM abstractions, ensuring the value remains synchronized between the C core and Rust code and preventing future maintenance issues. Signed-off-by: Michal Wilczynski Link: https://lore.kernel.org/r/20250702-rust-next-pwm-working-fan-for-sending-v7-1-67ef39ff1d29@samsung.com Signed-off-by: Uwe Kleine-König