From 51c1064e82e77b39a49889287ca50709303e2f26 Mon Sep 17 00:00:00 2001 From: Bartosz Golaszewski Date: Fri, 22 Nov 2019 15:19:21 +0100 Subject: gpiolib: add new ioctl() for monitoring changes in line info Currently there is no way for user-space to be informed about changes in status of GPIO lines e.g. when someone else requests the line or its config changes. We can only periodically re-read the line-info. This is fine for simple one-off user-space tools, but any daemon that provides a centralized access to GPIO chips would benefit hugely from an event driven line info synchronization. This patch adds a new ioctl() that allows user-space processes to reuse the file descriptor associated with the character device for watching any changes in line properties. Every such event contains the updated line information. Currently the events are generated on three types of status changes: when a line is requested, when it's released and when its config is changed. The first two are self-explanatory. For the third one: this will only happen when another user-space process calls the new SET_CONFIG ioctl() as any changes that can happen from within the kernel (i.e. set_transitory() or set_debounce()) are of no interest to user-space. Signed-off-by: Bartosz Golaszewski Reviewed-by: Linus Walleij --- include/uapi/linux/gpio.h | 30 ++++++++++++++++++++++++++++++ 1 file changed, 30 insertions(+) (limited to 'include/uapi') diff --git a/include/uapi/linux/gpio.h b/include/uapi/linux/gpio.h index 799cf823d493..dca320764e4d 100644 --- a/include/uapi/linux/gpio.h +++ b/include/uapi/linux/gpio.h @@ -59,6 +59,34 @@ struct gpioline_info { /* Maximum number of requested handles */ #define GPIOHANDLES_MAX 64 +/* Possible line status change events */ +enum { + GPIOLINE_CHANGED_REQUESTED = 1, + GPIOLINE_CHANGED_RELEASED, + GPIOLINE_CHANGED_CONFIG, +}; + +/** + * struct gpioline_info_changed - Information about a change in status + * of a GPIO line + * @info: updated line information + * @timestamp: estimate of time of status change occurrence, in nanoseconds + * and GPIOLINE_CHANGED_CONFIG + * @event_type: one of GPIOLINE_CHANGED_REQUESTED, GPIOLINE_CHANGED_RELEASED + * + * Note: struct gpioline_info embedded here has 32-bit alignment on its own, + * but it works fine with 64-bit alignment too. With its 72 byte size, we can + * guarantee there are no implicit holes between it and subsequent members. + * The 20-byte padding at the end makes sure we don't add any implicit padding + * at the end of the structure on 64-bit architectures. + */ +struct gpioline_info_changed { + struct gpioline_info info; + __u64 timestamp; + __u32 event_type; + __u32 padding[5]; /* for future use */ +}; + /* Linerequest flags */ #define GPIOHANDLE_REQUEST_INPUT (1UL << 0) #define GPIOHANDLE_REQUEST_OUTPUT (1UL << 1) @@ -176,6 +204,8 @@ struct gpioevent_data { #define GPIO_GET_CHIPINFO_IOCTL _IOR(0xB4, 0x01, struct gpiochip_info) #define GPIO_GET_LINEINFO_IOCTL _IOWR(0xB4, 0x02, struct gpioline_info) +#define GPIO_GET_LINEINFO_WATCH_IOCTL _IOWR(0xB4, 0x0b, struct gpioline_info) +#define GPIO_GET_LINEINFO_UNWATCH_IOCTL _IOWR(0xB4, 0x0c, __u32) #define GPIO_GET_LINEHANDLE_IOCTL _IOWR(0xB4, 0x03, struct gpiohandle_request) #define GPIO_GET_LINEEVENT_IOCTL _IOWR(0xB4, 0x04, struct gpioevent_request) -- cgit v1.2.3 From 32f5f62d7991c62095ee62a060b35dec0a9ac404 Mon Sep 17 00:00:00 2001 From: Jonathan Neuschäfer Date: Tue, 3 Mar 2020 21:01:48 +0100 Subject: gpio: uapi: Improve phrasing around arrays representing empty strings Character arrays can be considered empty strings (if they are immediately terminated), but they cannot be NULL. Signed-off-by: Jonathan Neuschäfer Signed-off-by: Bartosz Golaszewski --- include/uapi/linux/gpio.h | 8 ++++---- 1 file changed, 4 insertions(+), 4 deletions(-) (limited to 'include/uapi') diff --git a/include/uapi/linux/gpio.h b/include/uapi/linux/gpio.h index dca320764e4d..0206383c0383 100644 --- a/include/uapi/linux/gpio.h +++ b/include/uapi/linux/gpio.h @@ -18,7 +18,7 @@ * struct gpiochip_info - Information about a certain GPIO chip * @name: the Linux kernel name of this GPIO chip * @label: a functional name for this GPIO chip, such as a product - * number, may be NULL + * number, may be empty * @lines: number of GPIO lines on this chip */ struct gpiochip_info { @@ -44,10 +44,10 @@ struct gpiochip_info { * @flags: various flags for this line * @name: the name of this GPIO line, such as the output pin of the line on the * chip, a rail or a pin header name on a board, as specified by the gpio - * chip, may be NULL + * chip, may be empty * @consumer: a functional name for the consumer of this GPIO line as set by - * whatever is using it, will be NULL if there is no current user but may - * also be NULL if the consumer doesn't set this up + * whatever is using it, will be empty if there is no current user but may + * also be empty if the consumer doesn't set this up */ struct gpioline_info { __u32 line_offset; -- cgit v1.2.3